[PATCH] checkpatch: ignore /dev/null being added for file path checks

[Jonas Gorski <jonas.gorski@gmail.com>]

In e.g. schema to yaml conversion patches, a file may be deleted,
causing checkpatch in strict mode to complain about files outside of the
bindings directory being modified:

  ./scripts/checkpatch.pl --strict --showfile 0001-dt-bindings-spi-convert-spi-brcm63xx.txt-to-YAML.patch
  dev/null:72: WARNING: DT binding docs and includes should be a separate patch. See: Documentation/devicetree/bindings/submitting-patches.rst
  total: 0 errors, 1 warnings, 0 checks, 79 lines checked

Since this isn't a real file, skip any further checks based on the
file's location.

Fixes: 133712a2ec84 ("checkpatch: DT bindings should be a separate patch")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 880fde13d9b8..30de47909460 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2856,6 +2856,12 @@ sub process {
 			$realfile =~ s@^([^/]*)/@@ if (!$file);
 			$in_commit_log = 0;
 
+			# "/dev/null" being added means a file was actually
+			# deleted, no need for further file location checks
+			if ($line eq "+++ /dev/null") {
+				next;
+			}
+
 			$p1_prefix = $1;
 			if (!$file && $tree && $p1_prefix ne '' &&
 			    -e "$root/$p1_prefix") {
-- 
2.34.1