They need to have the class SERIAL.

Note: it is a Win 7 panel, not Win 8 certified.
Signed-off-by: NTomas Sokorai <tsokorai@gmail.com>
Signed-off-by: NBenjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>