checkpatch: add option for excluding directories

when importing code from external sources, we do not want to fail
on checkpatch and want to run full sanity checks.

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.

Change-Id: I7d321e85eed6bc37d5c6879ae88e21d20028a433
Signed-off-by: Anas Nashif <anas.nashif@intel.com>

scripts/checkpatch.pl

@@ -42,6 +42,7 @@ 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;
@@ -72,6 +73,7 @@ Options:
   --subjective, --strict     enable more subjective tests
   --types TYPE(,TYPE2...)    show only these comma separated message types
   --ignore TYPE(,TYPE2...)   ignore various comma separated message types
+  --exclude DIR(,DIR22...)   exclude directories
   --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
   --show-types               show the message "types" in the output
@@ -144,6 +146,7 @@ GetOptions(
 	'subjective!'	=> \$check,
 	'strict!'	=> \$check,
 	'ignore=s'	=> \@ignore,
+	'exclude=s'	=> \@exclude,
 	'types=s'	=> \@use,
 	'show-types!'	=> \$show_types,
 	'max-line-length=i' => \$max_line_length,
@@ -2186,6 +2189,15 @@ 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) {