migration-guides: add notes on FILE_LAYERNAME

(From yocto-docs rev: 3cc9f7a14815698c08f47ef5fe8c731b2c2ecf84)

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

documentation/migration-guides/migration-4.3.rst

@@ -26,6 +26,16 @@ no longer the default supported configuration. This setting does not affect whic
 kernel versions SDKs will run against and does not affect which versions of the kernel
 can be used to run builds.
 
+Layername override implications
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Code can now know which layer a recipe is coming from through the newly added
+:term:`FILE_LAYERNAME` variable and the ``layer-<layername> override``. This is being used
+for enabling QA checks on a per layer basis. For existing code this has the
+side effect that the QA checks will apply to things being bbappended to recipes
+from other layers. Those other layers would need to have patch upstream status
+entries for patches being bbappended for example.
+
 .. _migration-4.3-supported-distributions:
 
 Supported distributions

documentation/migration-guides/release-notes-4.3.rst

@@ -17,6 +17,18 @@ New Features / Enhancements in 4.3
 
    -  :term:`KERNEL_DTBVENDORED`: whether to keep vendor subdirectories.
 
+   -  :term:`FILE_LAYERNAME`: bitbake now sets this to the name of the layer containing the recipe
+
+- Layername functionality available through overrides
+
+  Code can now know which layer a recipe is coming from through the newly added :term:`FILE_LAYERNAME`
+  variable. This has been added as an override of the form ``layer-<layername>``. In particular,
+  this means QA checks can now be layer specific, for example::
+
+    ERROR_QA:layer-core:append = " patch-status"
+
+  which will enable the ``patch-status`` QA check for the core layer.
+
 -  Architecture-specific enhancements:
 
 -  Kernel-related enhancements: