include: uapi: serial: add support of rts delays in nanoseconds

Add support of rs485 delay in nanoseconds.

With fast data rates (1Mbaut or more), 1ms become quite long. Users need
to be able to set shorter delays than 1 ms in order not to slow down the
channel unnecessarily. This enables faster communication channels without
changing the baudrate.

Signed-off-by: Erwan Le Ray <erwan.leray@st.com>
Change-Id: I5ec757517be3da22e08df4cc622d08cb28544862

Author: Erwan Le Ray

include/uapi/linux/serial.h

@@ -128,6 +128,8 @@ struct serial_rs485 {
 							   (if supported) */
 	__u32	delay_rts_before_send;	/* Delay before send (milliseconds) */
 	__u32	delay_rts_after_send;	/* Delay after send (milliseconds) */
+	__u32	delay_rts_before_send_ns;	/* Delay (nanoseconds) */
+	__u32	delay_rts_after_send_ns;	/* Delay (nanoseconds) */
 	__u32	padding[5];		/* Memory is cheap, new structs
 					   are a royal PITA .. */
 };