test-manual/ptest: link to common framework ptest classes

We document how to add ptest support for a recipe by inheriting the
ptest class. We may as well tell the user to inherit a ptest class for a
common framework which does most of the job for you.

Suggested-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
(From yocto-docs rev: 411b18e489a97ea4cde05613cdd4c86deb0cb8cb)

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

documentation/test-manual/ptest.rst

@@ -61,6 +61,20 @@ test. Here is what you have to do for each recipe:
 
       inherit ptest
 
+   .. note::
+
+      Classes for common frameworks already exist in :term:`OpenEmbedded-Core
+      (OE-Core)`, such as:
+
+      -  :oe_git:`go-ptest </openembedded-core/tree/meta/classes-recipe/go-ptest.bbclass>`
+      -  :ref:`ref-classes-ptest-cargo`
+      -  :ref:`ref-classes-ptest-gnome`
+      -  :oe_git:`ptest-perl </openembedded-core/tree/meta/classes-recipe/ptest-perl.bbclass>`
+      -  :oe_git:`ptest-python-pytest </openembedded-core/tree/meta/classes-recipe/ptest-python-pytest.bbclass>`
+
+      Inheriting these classes with the ``inherit`` keyword in your recipe will
+      make the next steps automatic.
+
 -  *Create run-ptest:* This script starts your test. Locate the
    script where you will refer to it using
    :term:`SRC_URI`. Here is an