rpmsg: Introduce a driver override mechanism

Similar to other subsystems it's useful to provide a mechanism to force
a specific driver match on a device, so introduce this.
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/rpmsg_core.c

@@ -315,6 +315,9 @@ static int rpmsg_dev_match(struct device *dev, struct device_driver *drv)
 	const struct rpmsg_device_id *ids = rpdrv->id_table;
 	unsigned int i;
 
+	if (rpdev->driver_override)
+		return !strcmp(rpdev->driver_override, drv->name);
+
 	if (ids)
 		for (i = 0; ids[i].name[0]; i++)
 			if (rpmsg_id_match(rpdev, &ids[i]))

include/linux/rpmsg.h

@@ -64,6 +64,7 @@ struct rpmsg_channel_info {
  * rpmsg_device - device that belong to the rpmsg bus
  * @dev: the device struct
  * @id: device id (used to match between rpmsg drivers and devices)
+ * @driver_override: driver name to force a match
  * @src: local address
  * @dst: destination address
  * @ept: the rpmsg endpoint of this channel
@@ -72,6 +73,7 @@ struct rpmsg_channel_info {
 struct rpmsg_device {
 	struct device dev;
 	struct rpmsg_device_id id;
+	char *driver_override;
 	u32 src;
 	u32 dst;
 	struct rpmsg_endpoint *ept;