serial_core: Add wake_peer uart operation which is called before starting UART TX. The idea here is to provide a mechanism where we can wakeup our peer before sending data.

Signed-off-by: San Mehat <san@google.com>

drivers/serial/serial_core.c

@@ -94,6 +94,9 @@ static void __uart_start(struct tty_struct *tty)
 	struct uart_state *state = tty->driver_data;
 	struct uart_port *port = state->uart_port;
 
+	if (port->ops->wake_peer)
+		port->ops->wake_peer(port);
+
 	if (!uart_circ_empty(&state->xmit) && state->xmit.buf &&
 	    !tty->stopped && !tty->hw_stopped)
 		port->ops->start_tx(port);

include/linux/serial_core.h

@@ -234,6 +234,7 @@ struct uart_ops {
 	void		(*pm)(struct uart_port *, unsigned int state,
 			      unsigned int oldstate);
 	int		(*set_wake)(struct uart_port *, unsigned int state);
+	void		(*wake_peer)(struct uart_port *);
 
 	/*
 	 * Return a string describing the type of the port