ref-manual, overview-manual, Makefile: Moved toolchain concepts

Fixes [YOCTO #12370]

Moved the "Cross-Development Toolchain Generation" section from the
ref-manual to the overview-manual into the concepts chapter.  This
information is conceptual and now needs to live in the concepts
chapter of the new overview-manual.  Moving the section caused a
few links to have to be fixed in the ref-manual.  There was also a
figure in the section.  So, I had to move the figure from the ref-manual
to the overview-manual "figures" folder and update the Makefile for
the TARFILE generation.

(From yocto-docs rev: 1f3ee5ab308cbe6bd7194086026db397b67ca7c4)

Signed-off-by: Scott Rifenbark <srifenbark@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

3 files changed, 220 insertions, 4 deletions

diff --git a/documentation/overview-manual/figures/cross-development-toolchains.png b/documentation/overview-manual/figures/cross-development-toolchains.png
new file mode 100644
index 0000000000..d36670a198
--- /dev/null
+++ b/documentation/overview-manual/figures/cross-development-toolchains.png
diff --git a/documentation/overview-manual/overview-concepts.xml b/documentation/overview-manual/overview-concepts.xml
index aa8d35e3f9..0a45cd7256 100644
--- a/documentation/overview-manual/overview-concepts.xml
+++ b/documentation/overview-manual/overview-concepts.xml
@@ -255,6 +255,222 @@
         </section>
     </section>
 
+    <section id="cross-development-toolchain-generation">
+        <title>Cross-Development Toolchain Generation</title>
+
+        <para>
+            The Yocto Project does most of the work for you when it comes to
+            creating
+            <ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain'>cross-development toolchains</ulink>.
+            This section provides some technical background on how
+            cross-development toolchains are created and used.
+            For more information on toolchains, you can also see the
+            <ulink url='&YOCTO_DOCS_SDK_URL;'>Yocto Project Application Development and the Extensible Software Development Kit (eSDK)</ulink>
+            manual.
+        </para>
+
+        <para>
+            In the Yocto Project development environment, cross-development
+            toolchains are used to build the image and applications that run
+            on the target hardware.
+            With just a few commands, the OpenEmbedded build system creates
+            these necessary toolchains for you.
+        </para>
+
+        <para>
+            The following figure shows a high-level build environment regarding
+            toolchain construction and use.
+        </para>
+
+        <para>
+            <imagedata fileref="figures/cross-development-toolchains.png" width="8in" depth="6in" align="center" />
+        </para>
+
+        <para>
+            Most of the work occurs on the Build Host.
+            This is the machine used to build images and generally work within the
+            the Yocto Project environment.
+            When you run BitBake to create an image, the OpenEmbedded build system
+            uses the host <filename>gcc</filename> compiler to bootstrap a
+            cross-compiler named <filename>gcc-cross</filename>.
+            The <filename>gcc-cross</filename> compiler is what BitBake uses to
+            compile source files when creating the target image.
+            You can think of <filename>gcc-cross</filename> simply as an
+            automatically generated cross-compiler that is used internally within
+            BitBake only.
+            <note>
+                The extensible SDK does not use
+                <filename>gcc-cross-canadian</filename> since this SDK
+                ships a copy of the OpenEmbedded build system and the sysroot
+                within it contains <filename>gcc-cross</filename>.
+            </note>
+        </para>
+
+        <para>
+            The chain of events that occurs when <filename>gcc-cross</filename> is
+            bootstrapped is as follows:
+            <literallayout class='monospaced'>
+     gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> glibc-initial -> glibc -> gcc-cross -> gcc-runtime
+            </literallayout>
+            <itemizedlist>
+                <listitem><para>
+                    <filename>gcc</filename>:
+                    The build host's GNU Compiler Collection (GCC).
+                    </para></listitem>
+                <listitem><para>
+                    <filename>binutils-cross</filename>:
+                    The bare minimum binary utilities needed in order to run
+                    the <filename>gcc-cross-initial</filename> phase of the
+                    bootstrap operation.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>gcc-cross-initial</filename>:
+                    An early stage of the bootstrap process for creating
+                    the cross-compiler.
+                    This stage builds enough of the <filename>gcc-cross</filename>,
+                    the C library, and other pieces needed to finish building the
+                    final cross-compiler in later stages.
+                    This tool is a "native" package (i.e. it is designed to run on
+                    the build host).
+                    </para></listitem>
+                <listitem><para>
+                    <filename>linux-libc-headers</filename>:
+                    Headers needed for the cross-compiler.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>glibc-initial</filename>:
+                    An initial version of the Embedded GLIBC needed to bootstrap
+                    <filename>glibc</filename>.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>gcc-cross</filename>:
+                    The final stage of the bootstrap process for the
+                    cross-compiler.
+                    This stage results in the actual cross-compiler that
+                    BitBake uses when it builds an image for a targeted
+                    device.
+                    <note>
+                        If you are replacing this cross compiler toolchain
+                        with a custom version, you must replace
+                        <filename>gcc-cross</filename>.
+                    </note>
+                    This tool is also a "native" package (i.e. it is
+                    designed to run on the build host).
+                    </para></listitem>
+                <listitem><para>
+                    <filename>gcc-runtime</filename>:
+                    Runtime libraries resulting from the toolchain bootstrapping
+                    process.
+                    This tool produces a binary that consists of the
+                    runtime libraries need for the targeted device.
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+
+        <para>
+            You can use the OpenEmbedded build system to build an installer for
+            the relocatable SDK used to develop applications.
+            When you run the installer, it installs the toolchain, which contains
+            the development tools (e.g., the
+            <filename>gcc-cross-canadian</filename>),
+            <filename>binutils-cross-canadian</filename>, and other
+            <filename>nativesdk-*</filename> tools,
+            which are tools native to the SDK (i.e. native to
+            <ulink url='&YOCTO_DOCS_REF_URL;#var-SDK_ARCH'><filename>SDK_ARCH</filename></ulink>),
+            you need to cross-compile and test your software.
+            The figure shows the commands you use to easily build out this
+            toolchain.
+            This cross-development toolchain is built to execute on the
+            <ulink url='&YOCTO_DOCS_REF_URL;#var-SDKMACHINE'><filename>SDKMACHINE</filename></ulink>,
+            which might or might not be the same
+            machine as the Build Host.
+            <note>
+                If your target architecture is supported by the Yocto Project,
+                you can take advantage of pre-built images that ship with the
+                Yocto Project and already contain cross-development toolchain
+                installers.
+            </note>
+        </para>
+
+        <para>
+            Here is the bootstrap process for the relocatable toolchain:
+            <literallayout class='monospaced'>
+     gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers ->
+        glibc-initial -> nativesdk-glibc -> gcc-crosssdk -> gcc-cross-canadian
+            </literallayout>
+            <itemizedlist>
+                <listitem><para>
+                    <filename>gcc</filename>:
+                    The build host's GNU Compiler Collection (GCC).
+                    </para></listitem>
+                <listitem><para>
+                    <filename>binutils-crosssdk</filename>:
+                    The bare minimum binary utilities needed in order to run
+                    the <filename>gcc-crosssdk-initial</filename> phase of the
+                    bootstrap operation.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>gcc-crosssdk-initial</filename>:
+                    An early stage of the bootstrap process for creating
+                    the cross-compiler.
+                    This stage builds enough of the
+                    <filename>gcc-crosssdk</filename> and supporting pieces so that
+                    the final stage of the bootstrap process can produce the
+                    finished cross-compiler.
+                    This tool is a "native" binary that runs on the build host.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>linux-libc-headers</filename>:
+                    Headers needed for the cross-compiler.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>glibc-initial</filename>:
+                    An initial version of the Embedded GLIBC needed to bootstrap
+                    <filename>nativesdk-glibc</filename>.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>nativesdk-glibc</filename>:
+                    The Embedded GLIBC needed to bootstrap the
+                    <filename>gcc-crosssdk</filename>.
+                    </para></listitem>
+                <listitem><para>
+                    <filename>gcc-crosssdk</filename>:
+                    The final stage of the bootstrap process for the
+                    relocatable cross-compiler.
+                    The <filename>gcc-crosssdk</filename> is a transitory compiler
+                    and never leaves the build host.
+                    Its purpose is to help in the bootstrap process to create the
+                    eventual relocatable <filename>gcc-cross-canadian</filename>
+                    compiler, which is relocatable.
+                    This tool is also a "native" package (i.e. it is
+                    designed to run on the build host).
+                    </para></listitem>
+                <listitem><para>
+                    <filename>gcc-cross-canadian</filename>:
+                    The final relocatable cross-compiler.
+                    When run on the
+                    <ulink url='&YOCTO_DOCS_REF_URL;#var-SDKMACHINE'><filename>SDKMACHINE</filename></ulink>,
+                    this tool
+                    produces executable code that runs on the target device.
+                    Only one cross-canadian compiler is produced per architecture
+                    since they can be targeted at different processor optimizations
+                    using configurations passed to the compiler through the
+                    compile commands.
+                    This circumvents the need for multiple compilers and thus
+                    reduces the size of the toolchains.
+                    </para></listitem>
+            </itemizedlist>
+        </para>
+
+        <note>
+            For information on advantages gained when building a
+            cross-development toolchain installer, see the
+            "<ulink url='&YOCTO_DOCS_SDK_URL;#sdk-building-an-sdk-installer'>Building an SDK Installer</ulink>"
+            section in the Yocto Project Application Development and the
+            Extensible Software Development Kit (eSDK) manual.
+        </note>
+    </section>
+
     <section id='x32'>
         <title>x32 psABI</title>
 
diff --git a/documentation/overview-manual/overview-development-environment.xml b/documentation/overview-manual/overview-development-environment.xml
index d34f35ec88..62f3ccd438 100644
--- a/documentation/overview-manual/overview-development-environment.xml
+++ b/documentation/overview-manual/overview-development-environment.xml
@@ -2426,8 +2426,8 @@
             <note>
                 For more information on the cross-development toolchain
                 generation, see the
-                "<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>"
-                section in the Yocto Project Reference Manual.
+                "<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
+                section.
                 For information on advantages gained when building a
                 cross-development toolchain using the
                 <ulink url='&YOCTO_DOCS_REF_URL;#ref-tasks-populate_sdk'><filename>do_populate_sdk</filename></ulink>
@@ -2792,8 +2792,8 @@
                 <listitem><para>
                     For background information on cross-development toolchains
                     in the Yocto Project development environment, see the
-                    "<ulink url='&YOCTO_DOCS_REF_URL;#cross-development-toolchain-generation'>Cross-Development Toolchain Generation</ulink>"
-                    section in the Yocto Project Reference Manual.
+                    "<link linkend='cross-development-toolchain-generation'>Cross-Development Toolchain Generation</link>"
+                    section.
                     </para></listitem>
                 <listitem><para>
                     For information on setting up a cross-development