ref-manual: improve documentation for kernel-devicetree class

- Document the new KERNEL_DTBDEST and KERNEL_DTBVENDORED variables
- Also document the related KERNEL_DEVICETREE_BUNDLE
  and KERNEL_PACKAGE_NAME variables

(From yocto-docs rev: 19f128e725da35234ec2c234c667ee7ff3d67d8d)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

2 files changed, 43 insertions, 0 deletions

diff --git a/documentation/ref-manual/classes.rst b/documentation/ref-manual/classes.rst
index 78174d51d1..e454a54537 100644
--- a/documentation/ref-manual/classes.rst
+++ b/documentation/ref-manual/classes.rst
@@ -1576,6 +1576,14 @@ Linux kernel compilation (including modules).
 The :ref:`ref-classes-kernel-devicetree` class, which is inherited by the
 :ref:`ref-classes-kernel` class, supports device tree generation.
 
+Its behavior is mainly controlled by the following variables:
+
+-  :term:`KERNEL_DEVICETREE_BUNDLE`: whether to bundle the kernel and device tree
+-  :term:`KERNEL_DTBDEST`: directory where to install DTB files
+-  :term:`KERNEL_DTBVENDORED`: whether to keep vendor subdirectories
+-  :term:`KERNEL_DTC_FLAGS`: flags for ``dtc``, the Device Tree Compiler
+-  :term:`KERNEL_PACKAGE_NAME`: base name of the kernel packages
+
 .. _ref-classes-kernel-fitimage:
 
 ``kernel-fitimage``
diff --git a/documentation/ref-manual/variables.rst b/documentation/ref-manual/variables.rst
index b7829ae7af..e213478326 100644
--- a/documentation/ref-manual/variables.rst
+++ b/documentation/ref-manual/variables.rst
@@ -4451,6 +4451,16 @@ system and gives an overview of their function and contents.
       In order to use this variable, the :ref:`ref-classes-kernel-devicetree`
       class must be inherited.
 
+   :term:`KERNEL_DEVICETREE_BUNDLE`
+      When set to "1", this variable allows to bundle the Linux kernel
+      and the Device Tree Binary together in a single file.
+
+      This feature is currently only supported on the "arm" (32 bit)
+      architecture.
+
+      This variable is set to "0" by default by the
+      :ref:`ref-classes-kernel-devicetree` class.
+
    :term:`KERNEL_DTB_LINK_NAME`
       The link name of the kernel device tree binary (DTB). This variable
       is set in the ``meta/classes-recipe/kernel-artifact-names.bbclass`` file as
@@ -4476,6 +4486,23 @@ system and gives an overview of their function and contents.
 
       See :term:`KERNEL_ARTIFACT_NAME` for additional information.
 
+   :term:`KERNEL_DTBDEST`
+      This variable, used by the :ref:`ref-classes-kernel-devicetree`
+      class, allows to change the installation directory of the DTB
+      (Device Tree Binary) files.
+
+      It is set by default to "${KERNEL_IMAGEDEST}" by the
+      :ref:`ref-classes-kernel` class.
+
+   :term:`KERNEL_DTBVENDORED`
+      This variable, used by the :ref:`ref-classes-kernel-devicetree`,
+      allows to ignore vendor subdirectories when installing DTB
+      (Device Tree Binary) files, when it is set to "false".
+
+      To keep vendor subdirectories, set this variable to "true".
+
+      It is set by default to "false" by the :ref:`ref-classes-kernel` class.
+
    :term:`KERNEL_DTC_FLAGS`
       Specifies the ``dtc`` flags that are passed to the Linux kernel build
       system when generating the device trees (via ``DTC_FLAGS`` environment
@@ -4624,6 +4651,14 @@ system and gives an overview of their function and contents.
       provide those module configurations, see the
       :term:`module_conf_* <module_conf>` variable.
 
+   :term:`KERNEL_PACKAGE_NAME`
+      Specifies the base name of the kernel packages, such as "kernel"
+      in the kernel packages such as "kernel-modules", "kernel-image" and
+      "kernel-dbg".
+
+      The default value for this variable is set to "kernel" by the
+      :ref:`ref-classes-kernel` class.
+
    :term:`KERNEL_PATH`
       The location of the kernel sources. This variable is set to the value
       of the :term:`STAGING_KERNEL_DIR` within the :ref:`ref-classes-module`