bitbake: doc: Document suffix for BBFILE_PRIORITY

(Bitbake rev: 08c340d97717e632c5185a52eec46d90359d4006)

Signed-off-by: Simon A. Eugster <simon.eu@gmail.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst

@@ -754,6 +754,10 @@ overview of their function and contents.
    :term:`BBFILE_PRIORITY`
       Assigns the priority for recipe files in each layer.
 
+      This variable is used in the ``conf/layer.conf`` file and must be
+      suffixed with a `_` followed by the name of the specific layer (e.g.
+      ``BBFILE_PRIORITY_emenlow``). Colon as separator is not supported.
+
       This variable is useful in situations where the same recipe appears
       in more than one layer. Setting this variable allows you to
       prioritize a layer against other layers that contain the same recipe
@@ -768,7 +772,7 @@ overview of their function and contents.
       higher precedence. For example, the value 6 has a higher precedence
       than the value 5. If not specified, the :term:`BBFILE_PRIORITY` variable
       is set based on layer dependencies (see the :term:`LAYERDEPENDS` variable
-      for more information. The default priority, if unspecified for a
+      for more information). The default priority, if unspecified for a
       layer with no dependencies, is the lowest defined priority + 1 (or 1
       if no priorities are defined).