checkpatch: test for non-standard signatures

Warn on non-standard signature styles.
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -1600,13 +1600,17 @@ sub process {
 
 # Check signature styles
 		if (!$in_header_lines &&
-		    $line =~ /^(\s*)($signature_tags)(\s*)(.*)/) {
+		    $line =~ /^(\s*)([a-z0-9_-]+by:|$signature_tags)(\s*)(.*)/i) {
 			my $space_before = $1;
 			my $sign_off = $2;
 			my $space_after = $3;
 			my $email = $4;
 			my $ucfirst_sign_off = ucfirst(lc($sign_off));
 
+			if ($sign_off !~ /$signature_tags/) {
+				WARN("BAD_SIGN_OFF",
+				     "Non-standard signature: $sign_off\n" . $herecurr);
+			}
 			if (defined $space_before && $space_before ne "") {
 				WARN("BAD_SIGN_OFF",
 				     "Do not use whitespace before $ucfirst_sign_off\n" . $herecurr);