[PATCH] Serial: Add uart_insert_char()

Add uart_insert_char(), which handles inserting characters into the
flip buffer.  This helper function handles the correct semantics
for handling overrun in addition to inserting normal characters.

Signed-off-by: Russell King <rmk@arm.linux.org.uk>
diff --git a/drivers/serial/sa1100.c b/drivers/serial/sa1100.c
index 157218b..22565a6 100644
--- a/drivers/serial/sa1100.c
+++ b/drivers/serial/sa1100.c
@@ -237,10 +237,7 @@
 		if (uart_handle_sysrq_char(&sport->port, ch, regs))
 			goto ignore_char;
 
-		if ((status & port->ignore_status_mask & ~UTSR1_TO_SM(UTSR1_ROR)) == 0)
-			tty_insert_flip_char(tty, ch, flg);
-		if (status & ~port->ignore_status_mask & UTSR1_TO_SM(UTSR1_ROR))
-			tty_insert_flip_char(tty, 0, TTY_OVERRUN);
+		uart_insert_char(&sport->port, status, UTSR1_TO_SM(UTSR1_ROR), ch, flg);
 
 	ignore_char:
 		status = UTSR1_TO_SM(UART_GET_UTSR1(sport)) |