device connection: Add fwnode member to struct device_connection

This will prepare the device connection API for connections
described in firmware.
Acked-by: NHans de Goede <hdegoede@redhat.com>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: NJun Li <jun.li@nxp.com>
Signed-off-by: NHeikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/device.h

@@ -757,11 +757,17 @@ struct device_dma_parameters {
 
 /**
  * struct device_connection - Device Connection Descriptor
+ * @fwnode: The device node of the connected device
  * @endpoint: The names of the two devices connected together
  * @id: Unique identifier for the connection
  * @list: List head, private, for internal use only
+ *
+ * NOTE: @fwnode is not used together with @endpoint. @fwnode is used when
+ * platform firmware defines the connection. When the connection is registered
+ * with device_connection_add() @endpoint is used instead.
  */
 struct device_connection {
+	struct fwnode_handle	*fwnode;
 	const char		*endpoint[2];
 	const char		*id;
 	struct list_head	list;