checkpatch.pl: check for the FSF mailing address

Kernel maintainers reject new instances of the GPL boilerplate paragraph
directing people to write to the FSF for a copy of the GPL, since the FSF
has moved in the past and may do so again.

Make this an error for new code, but just a --strict CHK in --file mode;
anyone interested in doing tree-wide cleanups of this form can enable this
test explicitly.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-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

@@ -1962,6 +1962,18 @@ sub process {
 			$rpt_cleaners = 1;
 		}
 
+# Check for FSF mailing addresses.
+		if ($rawline =~ /You should have received a copy/ ||
+		    $rawline =~ /write to the Free Software/ ||
+		    $rawline =~ /59 Temple Place/ ||
+		    $rawline =~ /51 Franklin Street/) {
+			my $herevet = "$here\n" . cat_vet($rawline) . "\n";
+			my $msg_type = \&ERROR;
+			$msg_type = \&CHK if ($file);
+			&{$msg_type}("FSF_MAILING_ADDRESS",
+				"Do not include the paragraph about writing to the Free Software Foundation's mailing address from the sample GPL notice. The FSF has changed addresses in the past, and may do so again. Linux already includes a copy of the GPL.\n" . $herevet)
+		}
+
 # check for Kconfig help text having a real description
 # Only applies when adding the entry originally, after that we do not have
 # sufficient context to determine whether it is indeed long enough.