serial: doc: .(un)throttle() depends on hardware assisted flow control

Document that .throttle() and .unthrottle() are relevant only if
hardware assisted flow control is enabled.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/serial/driver b/Documentation/serial/driver
index 03369d0..03b703c 100644 (file)
--- a/Documentation/serial/driver
+++ b/Documentation/serial/driver
@@ -135,6 +135,7 @@ hardware.
        Notify the serial driver that input buffers for the line discipline are
        close to full, and it should somehow signal that no more characters
        should be sent to the serial port.
+       This will be called only if hardware assisted flow control is enabled.
 
        Locking: none.
 
@@ -142,6 +143,7 @@ hardware.
        Notify the serial driver that characters can now be sent to the serial
        port without fear of overrunning the input buffers of the line
        disciplines.
+       This will be called only if hardware assisted flow control is enabled.
 
        Locking: none.