uti/lint/checkpatch: add --exclude to ignore specific directories

checkpatch: add option for excluding directories
when importing code from external sources

Using --exclude <dir> we should be able to exclude a list of well
defined locations in the tree that carry sources from other projects
with other styles.

This comes from the 01org/zephyr project in github:
Original-Change-Id: I7d321e85eed6bc37d5c6879ae88e21d20028a433
Original-Signed-off-by: Anas Nashif <anas.nashif@intel.com>

Change-Id: Icc9e841e7d84026d6ab857ff90b0f093515ccaad
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/18568
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>

util/lint/checkpatch.pl

@@ -45,6 +45,7 @@ my %use_type = ();
 my @use = ();
 my %ignore_type = ();
 my @ignore = ();
+my @exclude = ();
 my $help = 0;
 my $configuration_file = ".checkpatch.conf";
 my $max_line_length = 80;
@@ -86,6 +87,7 @@ Options:
   --list-types               list the possible message types
   --types TYPE(,TYPE2...)    show only these comma separated message types
   --ignore TYPE(,TYPE2...)   ignore various comma separated message types
+  --exclude DIR(,DIR22...)   exclude directories
   --show-types               show the specific message type in the output
   --max-line-length=n        set the maximum line length, if exceeded, warn
   --min-conf-desc-length=n   set the min description length, if shorter, warn
@@ -190,6 +192,7 @@ GetOptions(
 	'subjective!'	=> \$check,
 	'strict!'	=> \$check,
 	'ignore=s'	=> \@ignore,
+	'exclude=s'	=> \@exclude,
 	'types=s'	=> \@use,
 	'show-types!'	=> \$show_types,
 	'list-types!'	=> \$list_types,
@@ -2277,6 +2280,16 @@ sub process {
 			$found_file = 1;
 		}
 
+		my $skipme = 0;
+		foreach (@exclude) {
+			if ($realfile =~ m@^(?:$_/)@) {
+				$skipme = 1;
+			}
+		}
+		if ($skipme) {
+			next;
+		}
+
 #make up the handle for any error we report on this line
 		if ($showfile) {
 			$prefix = "$realfile:$realline: "