pps: Reserve a line discipline number for PPS

Add a new line discipline for "pulse per second" devices connected to
a serial port.
Signed-off-by: NRodolfo Giometti <giometti@linux.it>
Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/tty.h

@@ -23,7 +23,7 @@
  */
 #define NR_UNIX98_PTY_DEFAULT	4096      /* Default maximum for Unix98 ptys */
 #define NR_UNIX98_PTY_MAX	(1 << MINORBITS) /* Absolute limit */
-#define NR_LDISCS		18
+#define NR_LDISCS		19
 
 /* line disciplines */
 #define N_TTY		0
@@ -45,6 +45,7 @@
 #define N_HCI		15	/* Bluetooth HCI UART */
 #define N_GIGASET_M101	16	/* Siemens Gigaset M101 serial DECT adapter */
 #define N_SLCAN		17	/* Serial / USB serial CAN Adaptors */
+#define N_PPS		18	/* Pulse per Second */
 
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as