tty/serial: atmel: add fractional baud rate support

The USART device provides a fractional baud rate generator to get a more
accurate baud rate. It can be used only when the USART is configured in
'normal mode' and this feature is not available on AT91RM9200 SoC.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/atmel_serial.h b/include/linux/atmel_serial.h
index 5a4d664..f8e452a 100644
--- a/include/linux/atmel_serial.h
+++ b/include/linux/atmel_serial.h
@@ -118,6 +118,7 @@
 
 #define ATMEL_US_BRGR		0x20	/* Baud Rate Generator Register */
 #define	ATMEL_US_CD		GENMASK(15, 0)	/* Clock Divider */
+#define ATMEL_US_FP_OFFSET	16	/* Fractional Part */
 
 #define ATMEL_US_RTOR		0x24	/* Receiver Time-out Register for USART */
 #define ATMEL_UA_RTOR		0x28	/* Receiver Time-out Register for UART */