diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index 88ad615..77ba0af 100644
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -186,6 +186,17 @@
 	Locking: port_sem taken.
 	Interrupts: caller dependent.
 
+  flush_buffer(port)
+	Flush any write buffers, reset any DMA state and stop any
+	ongoing DMA transfers.
+
+	This will be called whenever the port->info->xmit circular
+	buffer is cleared.
+
+	Locking: port->lock taken.
+	Interrupts: locally disabled.
+	This call must not sleep
+
   set_termios(port,termios,oldtermios)
 	Change the port parameters, including word length, parity, stop
 	bits.  Update read_status_mask and ignore_status_mask to indicate
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index 42d2e10..9884bc9 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -573,6 +573,8 @@
 
 	spin_lock_irqsave(&port->lock, flags);
 	uart_circ_clear(&state->info->xmit);
+	if (port->ops->flush_buffer)
+		port->ops->flush_buffer(port);
 	spin_unlock_irqrestore(&port->lock, flags);
 	tty_wakeup(tty);
 }
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index d8f31de..1d2faa6 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -190,6 +190,7 @@
 	void		(*break_ctl)(struct uart_port *, int ctl);
 	int		(*startup)(struct uart_port *);
 	void		(*shutdown)(struct uart_port *);
+	void		(*flush_buffer)(struct uart_port *);
 	void		(*set_termios)(struct uart_port *, struct ktermios *new,
 				       struct ktermios *old);
 	void		(*set_ldisc)(struct uart_port *);