TTY: provide drivers with tty_port_install

This will be used in tty_ops->install to set tty->port (and to call
tty_standard_install).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 9f47ab5..45ef71d 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -521,6 +521,8 @@
 extern void tty_port_close_end(struct tty_port *port, struct tty_struct *tty);
 extern void tty_port_close(struct tty_port *port,
 				struct tty_struct *tty, struct file *filp);
+extern int tty_port_install(struct tty_port *port, struct tty_driver *driver,
+				struct tty_struct *tty);
 extern int tty_port_open(struct tty_port *port,
 				struct tty_struct *tty, struct file *filp);
 static inline int tty_port_users(struct tty_port *port)