[PATCH v5] checkpatch: introduce proper bindings license check

[Dmitry Rokosov]

All headers from 'include/dt-bindings/' must be verified by checkpatch
together with Documentation bindings, because all of them are part of
the whole DT bindings system.

The requirement is dual licensed and matching patterns:
* Schemas:
    /GPL-2\.0(?:-only)? OR BSD-2-Clause/
* Headers:
    /GPL-2\.0(?:-only)? OR \S+/

Above patterns suggested by Rob at:
https://lore.kernel.org/all/CAL_Jsq+-YJsBO+LuPJ=ZQ=eb-monrwzuCppvReH+af7hYZzNaQ@xxxxxxxxxxxxxx

The issue was found during patch review:
https://lore.kernel.org/all/20230313201259.19998-4-ddrokosov@xxxxxxxxxxxxxx/

Signed-off-by: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxx>
---
Changes v5 since v4 at [4]:
    - only capital OR is acceptable for SPDX per Rob's suggestion

Changes v4 since v3 at [3]:
    - introduce separate pattern for dt-bindings headers following Rob's
      suggestion

Changes v3 since v2 at [2]:
    - replace 'not =~' expression with '!~' to be aligned with other
      checkpatch lines

Changes v2 since v1 at [1]:
    - include/dt-bindings check is aligned to open parens
    - introduce more strict pattern for bindings license:
      /GPL-2\.0(?:-only|-or-later|\+)? (?:OR|or) BSD-2-Clause/

Links:
    [1] https://lore.kernel.org/all/20230317201621.15518-1-ddrokosov@xxxxxxxxxxxxxx/
    [2] https://lore.kernel.org/all/20230320100027.27788-1-ddrokosov@xxxxxxxxxxxxxx/
    [3] https://lore.kernel.org/all/20230320203350.13696-1-ddrokosov@xxxxxxxxxxxxxx/
    [4] https://lore.kernel.org/all/20230331121017.14324-1-ddrokosov@xxxxxxxxxxxxxx/
---
 scripts/checkpatch.pl | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 78cc595b98ce..7d9b63fffa9d 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3710,7 +3710,7 @@ sub process {
 						     "'$spdx_license' is not supported in LICENSES/...\n" . $herecurr);
 					}
 					if ($realfile =~ m@^Documentation/devicetree/bindings/@ &&
-					    not $spdx_license =~ /GPL-2\.0.*BSD-2-Clause/) {
+					    $spdx_license !~ /GPL-2\.0(?:-only)? OR BSD-2-Clause/) {
 						my $msg_level = \&WARN;
 						$msg_level = \&CHK if ($file);
 						if (&{$msg_level}("SPDX_LICENSE_TAG",
@@ -3720,6 +3720,11 @@ sub process {
 							$fixed[$fixlinenr] =~ s/SPDX-License-Identifier: .*/SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)/;
 						}
 					}
+					if ($realfile =~ m@^include/dt-bindings/@ &&
+					    $spdx_license !~ /GPL-2\.0(?:-only)? OR \S+/) {
+						WARN("SPDX_LICENSE_TAG",
+						     "DT binding headers should be licensed (GPL-2.0-only OR .*)\n" . $herecurr);
+					}
 				}
 			}
 		}
-- 
2.36.0