migration-5.3: replace kernel-fitimage by kernel-fit-image

Add migration documentation for users moving from the removed
kernel-fitimage.bbclass to the new kernel-fit-image.bbclass.

(From yocto-docs rev: 4c3552940a6ff89824845473317b7f5d741d4635)

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/migration-guides/migration-5.3.rst

@@ -59,6 +59,48 @@ Removed classes
 
 The following classes have been removed in this release:
 
+-  ``kernel-fitimage.bbclass``: the class has been replaced by the
+   :ref:`ref-classes-kernel-fit-image` class. The new implementation resolves
+   the long-standing :yocto_bugs:`bug 12912</show_bug.cgi?id=12912>`.
+
+   If you are using the kernel FIT image support, you will need to:
+
+   #. Make sure to include ``kernel-fit-extra-artifacts`` in your :term:`KERNEL_CLASSES`
+      variable to ensure the required files are exposed to the :term:`DEPLOY_DIR_IMAGE`
+      directory::
+
+         KERNEL_CLASSES += "kernel-fit-extra-artifacts"
+
+   #. Use the specific FIT image recipe rather than the base kernel recipe.
+      For example, instead of::
+
+         bitbake linux-yocto
+
+      the FIT image is now build by::
+
+         bitbake linux-yocto-fitimage
+
+      For custom kernel recipes, creating a corresponding custom FIT image recipe
+      is usually a good approach.
+
+   #. If a FIT image is used as a replacement for the kernel image in the root
+      filesystem, add the following configuration to your machine configuration
+      file::
+
+         # Create and deploy the vmlinux artifact which gets included into the FIT image
+         KERNEL_CLASSES += "kernel-fit-extra-artifacts"
+
+         # Do not install the kernel image package
+         RRECOMMENDS:${KERNEL_PACKAGE_NAME}-base = ""
+         # Install the FIT image package
+         MACHINE_ESSENTIAL_EXTRA_RDEPENDS += "linux-yocto-fitimage"
+
+         # Configure the image.bbclass to depend on the FIT image instead of only
+         # the kernel to ensure the FIT image is built and deployed with the image
+         KERNEL_DEPLOY_DEPEND = "linux-yocto-fitimage:do_deploy"
+
+   See the :ref:`ref-classes-kernel-fit-image` section for more information.
+
 Removed features
 ~~~~~~~~~~~~~~~~