doc: dev/ref manual: describe the <PKG>_PATCHES variable

Fixes: 2e2242356f0bc72a56bc ("ptxd_make_world_patchin: allow specifying a custom patch directory")
Signed-off-by: Roland Hieber <rhi@pengutronix.de>
Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>

2 files changed, 14 insertions, 1 deletions

diff --git a/doc/dev_manual.rst b/doc/dev_manual.rst
index c37094090..29d1cbf1d 100644
--- a/doc/dev_manual.rst
+++ b/doc/dev_manual.rst
@@ -1265,7 +1265,10 @@ integrated into your BSP or into PTXdist.
 
 PTXdist handles patching automatically.
 After extracting the archive of a package, PTXdist checks for the existence of
-a patch directory named like its ``<PKG>`` variable.
+a patch directory named like its ``<PKG>_PATCHES`` variable, or, if this variable
+is not set, like its ``<PKG>`` variable.
+The patch directory is then searched in all locations listed by the
+``PTXDIST_PATH_PATCHES`` variable, and the first one found is used.
 Take an exemplary package ``foo`` with version ``1.1.0``:
 The variable ``FOO`` will have the value ``foo-1.1.0``, so PTXdist will look for
 a patch directory named ``foo-1.1.0`` in the following locations:
diff --git a/doc/ref_make_variables.inc b/doc/ref_make_variables.inc
index 08854c7db..fcfac83d3 100644
--- a/doc/ref_make_variables.inc
+++ b/doc/ref_make_variables.inc
@@ -205,6 +205,16 @@ Package Definition
   For local URLs (``file://`` or ``lndir://``) ``<PKG>_SOURCE`` must not be
   set.
 
+``<PKG>_PATCHES``
+  The name of the patch directory, relative to any of the paths listed in
+  ``PTXDIST_PATH_PATCHES`` (i.e., according to the search order described in
+  :ref:`patching_packages`).
+  If not specified, the default patch directory name is set to the value of the
+  ``<PKG>`` variable.
+
+  This variable can be set for multiple packages that should share the same
+  patch stack (e.g. kernel packages).
+
 ``<PKG>_DIR``
   This is the directory where the source archive is extracted. In most
   cases this is set to ``$(BUILDDIR)/$(<PKG>)``. However, if two packages