diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index ba64e4b..c415b0e 100644
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -59,7 +59,9 @@
 access to the info->tmpbuf bouncebuffer used for port writes.
 
 The port_sem semaphore is used to protect against ports being added/
-removed or reconfigured at inappropriate times.
+removed or reconfigured at inappropriate times. Since v2.6.27, this
+semaphore has been the 'mutex' member of the tty_port struct, and
+commonly referred to as the port mutex (or port->mutex).
 
 
 uart_ops
@@ -248,7 +250,7 @@
 	Other flags may be used (eg, xon/xoff characters) if your
 	hardware supports hardware "soft" flow control.
 
-	Locking: none.
+	Locking: caller holds port->mutex
 	Interrupts: caller dependent.
 	This call must not sleep