tty: add kernel-doc for tty_port_operations

tty_port_operations used to have only comments along its members.
Convert them into proper kernel-doc comments in front of the structure.
And add some more explanation to them where needed.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211126081611.11001-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/tty_port.h

@@ -12,21 +12,28 @@ struct tty_driver;
 struct tty_port;
 struct tty_struct;
 
+/**
+ * struct tty_port_operations -- operations on tty_port
+ * @carrier_raised: return 1 if the carrier is raised on @port
+ * @dtr_rts: raise the DTR line if @raise is nonzero, otherwise lower DTR
+ * @shutdown: called when the last close completes or a hangup finishes IFF the
+ *	port was initialized. Do not use to free resources. Turn off the device
+ *	only. Called under the port mutex to serialize against @activate and
+ *	@shutdown.
+ * @activate: called under the port mutex from tty_port_open(), serialized using
+ *	the port mutex. Supposed to turn on the device.
+ *
+ *	FIXME: long term getting the tty argument *out* of this would be good
+ *	for consoles.
+ *
+ * @destruct: called on the final put of a port. Free resources, possibly incl.
+ *	the port itself.
+ */
 struct tty_port_operations {
-	/* Return 1 if the carrier is raised */
 	int (*carrier_raised)(struct tty_port *port);
-	/* Control the DTR line */
 	void (*dtr_rts)(struct tty_port *port, int raise);
-	/* Called when the last close completes or a hangup finishes
-	   IFF the port was initialized. Do not use to free resources. Called
-	   under the port mutex to serialize against activate/shutdowns */
 	void (*shutdown)(struct tty_port *port);
-	/* Called under the port mutex from tty_port_open, serialized using
-	   the port mutex */
-        /* FIXME: long term getting the tty argument *out* of this would be
-           good for consoles */
 	int (*activate)(struct tty_port *port, struct tty_struct *tty);
-	/* Called on the final put of a port */
 	void (*destruct)(struct tty_port *port);
 };