net: phy: fix up const issues in to_mdio_device() and to_phy_device()

Both to_mdio_device() and to_phy_device() "throw away" the const pointer
attribute passed to them and return a non-const pointer, which generally
is not a good thing overall.  Fix this up by using container_of_const()
which was designed for this very problem.

Cc: Alexander Lobakin <[email protected]>
Cc: Andrew Lunn <[email protected]>
Cc: Heiner Kallweit <[email protected]>
Cc: Russell King <[email protected]>
Fixes: 7eab14d ("mdio, phy: fix -Wshadow warnings triggered by nested container_of()")
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Link: https://patch.msgid.link/2025052246-conduit-glory-8fc9@gregkh
Signed-off-by: Jakub Kicinski <[email protected]>

Author: gregkh

include/linux/mdio.h

@@ -45,10 +45,7 @@ struct mdio_device {
 	unsigned int reset_deassert_delay;
 };
 
-static inline struct mdio_device *to_mdio_device(const struct device *dev)
-{
-	return container_of(dev, struct mdio_device, dev);
-}
+#define to_mdio_device(__dev)	container_of_const(__dev, struct mdio_device, dev)
 
 /* struct mdio_driver_common: Common to all MDIO drivers */
 struct mdio_driver_common {

include/linux/phy.h

@@ -744,10 +744,7 @@ struct phy_device {
 #define PHY_F_NO_IRQ		0x80000000
 #define PHY_F_RXC_ALWAYS_ON	0x40000000
 
-static inline struct phy_device *to_phy_device(const struct device *dev)
-{
-	return container_of(to_mdio_device(dev), struct phy_device, mdio);
-}
+#define to_phy_device(__dev)	container_of_const(to_mdio_device(__dev), struct phy_device, mdio)
 
 /**
  * struct phy_tdr_config - Configuration of a TDR raw test