dev-manual, ref-manual: Created new section on initramfs

Fixes [YOCTO #7096]

We did not document how to create an initramfs image to be included
with a kernel build.  Various variables sort of inferred the
knowledge.  I created a new section in the "Common Tasks" section
of the dev-manual that describes how to create an initramfs image.

Also, I updated the kernel.bbclass reference section to point back
to the new "how-to" section.

Finally, I also created a bunch of cross-reference links from various
related variables back to the new "how-to" section.

(From yocto-docs rev: 289dfbd5d24241e42446a043104eecd6dca76f13)

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

1 files changed, 16 insertions, 5 deletions

diff --git a/documentation/ref-manual/ref-classes.xml b/documentation/ref-manual/ref-classes.xml
index 2344a0406a..f7b1126d7c 100644
--- a/documentation/ref-manual/ref-classes.xml
+++ b/documentation/ref-manual/ref-classes.xml
@@ -1873,11 +1873,22 @@
     </para>
 
     <para>
-        This means that each built kernel module is packaged separately and inter-module
-        dependencies are created by parsing the <filename>modinfo</filename> output.
-        If all modules are required, then installing the <filename>kernel-modules</filename>
-        package installs all packages with modules and various other kernel packages
-        such as <filename>kernel-vmlinux</filename>.
+        This means that each built kernel module is packaged separately and
+        inter-module dependencies are created by parsing the
+        <filename>modinfo</filename> output.
+        If all modules are required, then installing the
+        <filename>kernel-modules</filename> package installs all packages with
+        modules and various other kernel packages such as
+        <filename>kernel-vmlinux</filename>.
+    </para>
+
+    <para>
+        The <filename>kernel</filename> class contains logic that allows
+        you to embed an initial RAM filesystem (initramfs) image when
+        you build the kernel image.
+        For information on how to build an initramfs, see the
+        "<ulink url='&YOCTO_DOCS_DEV_URL;#building-an-initramfs-image'>Building an Initial RAM Filesystem (initramfs) Image</ulink>"
+        section in the Yocto Project Development Manual.
     </para>
 
     <para>