driver core: Add fwnode_to_dev() to look up device from fwnode

It's often useful to look up a device that corresponds to a fwnode. So
add an API to do that irrespective of the bus on which the device has
been added to.

Signed-off-by: Saravana Kannan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/core.c

···
 					     BUS_NOTIFY_ADD_DEVICE, dev);
 
 	kobject_uevent(&dev->kobj, KOBJ_ADD);
+
+	if (dev->fwnode && !dev->fwnode->dev)
+		dev->fwnode->dev = dev;
+
 	bus_probe_device(dev);
 	if (parent)
 		klist_add_tail(&dev->p->knode_parent,
···
 	device_lock(dev);
 	kill_device(dev);
 	device_unlock(dev);
+
+	if (dev->fwnode && dev->fwnode->dev == dev)
+		dev->fwnode->dev = NULL;
 
 	/* Notify clients of device removal.  This call must come
 	 * before dpm_sysfs_remove().

include/linux/fwnode.h

···
 struct fwnode_handle {
 	struct fwnode_handle *secondary;
 	const struct fwnode_operations *ops;
+	struct device *dev;
 };
 
 /**
···
 		if (fwnode_has_op(fwnode, op))				\
 			(fwnode)->ops->op(fwnode, ## __VA_ARGS__);	\
 	} while (false)
+#define get_dev_from_fwnode(fwnode)	get_device((fwnode)->dev)
 
 #endif