docs/manual: add section about patch licensing

Use the same text that is used in COPYING.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Cc: Peter Korsgaard <peter@korsgaard.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Steve Calfee <stevecalfee@gmail.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

docs/manual/legal-notice.txt

@@ -134,11 +134,13 @@ Buildroot, with the name used in the manifest files:
   http://apache.org/licenses/LICENSE-2.0.html[
   Apache License, version 2.0];
 
+[[legal-info-buildroot]]
 === Complying with the Buildroot license
 
 Buildroot itself is an open source software, released under the
-http://www.gnu.org/licenses/old-licenses/gpl-2.0.html[GNU General Public
-License, version 2] or (at your option) any later version.
+http://www.gnu.org/licenses/old-licenses/gpl-2.0.html[GNU General
+Public License, version 2] or (at your option) any later version, with
+the exception of the package patches detailed below.
 However, being a build system, it is not normally part of the end product:
 if you develop the root filesystem, kernel, bootloader or toolchain for a
 device, the code of Buildroot is only present on the development machine, not
@@ -159,3 +161,14 @@ material that must be redistributed.
 
 Keep in mind that this is only the Buildroot developers' opinion, and you
 should consult your legal department or lawyer in case of any doubt.
+
+==== Patches to packages
+
+Buildroot also bundles patch files, which are applied to the sources
+of the various packages. Those patches are not covered by the license
+of Buildroot. Instead, they are covered by the license of the software
+to which the patches are applied. When said software is available
+under multiple licenses, the Buildroot patches are only provided under
+the publicly accessible licenses.
+
+See xref:patch-policy[] for the technical details.

docs/manual/patch-policy.txt

@@ -91,7 +91,7 @@ If something goes wrong in the steps _3_ or _4_, then the build fails.
 === Format and licensing of the package patches
 
 Patches are released under the same license as the software they apply
-to.
+to (see xref:legal-info-buildroot[]).
 
 A message explaining what the patch does, and why it is needed, should
 be added in the header commentary of the patch.