[PATCH v2] serial: add PORT_GENERIC definition

[Max Filippov <jcmvbkbc@gmail.com>]

Current pattern in the linux kernel is that every new serial driver adds
one or more new PORT_ definitions because uart_ops::config_port()
callback documentation prescribes setting port->type according to the
type of port found, or to PORT_UNKNOWN if no port was detected.

When the specific type of the port is not important to the userspace
there's no need for a unique PORT_ value, but so far there's no suitable
identifier for that case.

Provide generic port type identifier other than PORT_UNKNOWN for ports
which type is not important to userspace.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
Changes v1->v2:
- move to the end of PORT_ definition list
- rename to PORT_GENERIC

 include/uapi/linux/serial_core.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index add349889d0a..0a5090e08657 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -245,4 +245,7 @@
 /* Sunplus UART */
 #define PORT_SUNPLUS	123
 
+/* Generic type identifier for ports which type is not important to userspace. */
+#define PORT_GENERIC	(-1)
+
 #endif /* _UAPILINUX_SERIAL_CORE_H */
-- 
2.30.2