net: phy: Add swnode support to mdiobus_scan

This patch will allow to use a swnode/fwnode defined for a phy_device. The
MDIO bus (mii_bus) needs to contain nodes for the PHY devices, named
"ethernet-phy@i", with i being the MDIO address (0 .. PHY_MAX_ADDR - 1).

The fwnode is only attached to the phy_device if there isn't already an
fwnode attached.

fwnode_get_named_child_node will increase the usage counter of the fwnode.
However, no new code is needed to decrease the counter again, since this is
already implemented in the phy_device_release function.

Signed-off-by: Hans-Frieder Vogt <hfdevel@gmx.net>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250322-tn9510-v3a-v7-1-672a9a3d8628@gmx.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/mdio_bus.c

@@ -551,6 +551,8 @@ static int mdiobus_create_device(struct mii_bus *bus,
 static struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr, bool c45)
 {
 	struct phy_device *phydev = ERR_PTR(-ENODEV);
+	struct fwnode_handle *fwnode;
+	char node_name[16];
 	int err;
 
 	phydev = get_phy_device(bus, addr, c45);
@@ -562,6 +564,18 @@ static struct phy_device *mdiobus_scan(struct mii_bus *bus, int addr, bool c45)
 	 */
 	of_mdiobus_link_mdiodev(bus, &phydev->mdio);
 
+	/* Search for a swnode for the phy in the swnode hierarchy of the bus.
+	 * If there is no swnode for the phy provided, just ignore it.
+	 */
+	if (dev_fwnode(&bus->dev) && !dev_fwnode(&phydev->mdio.dev)) {
+		snprintf(node_name, sizeof(node_name), "ethernet-phy@%d",
+			 addr);
+		fwnode = fwnode_get_named_child_node(dev_fwnode(&bus->dev),
+						     node_name);
+		if (fwnode)
+			device_set_node(&phydev->mdio.dev, fwnode);
+	}
+
 	err = phy_device_register(phydev);
 	if (err) {
 		phy_device_free(phydev);