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>