net: stmmac: Deprecate snps, phy-addr and auto-detect PHY address

The snps,phy-addr device tree property is non-standard, and should be
removed in favor of proper phy node support. Remove it from the binding
documents and warn if the property is still used.

Most PHYs respond to address 0, but a few don't, so auto-detect PHY
address by default, to make up for the lack of explicit address selection.

Signed-off-by: Chen-Yu Tsai <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/devicetree/bindings/net/stmmac.txt

···
   property
 - phy-mode: String, operation mode of the PHY interface.
   Supported values are: "mii", "rmii", "gmii", "rgmii".
-- snps,phy-addr		phy address to connect to.
 - snps,reset-gpio 	gpio number for phy reset.
 - snps,reset-active-low boolean flag to indicate if phy reset is active low.
 - snps,reset-delays-us  is triplet of delays

drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c

···
 	if (plat->bus_id < 0)
 		plat->bus_id = 0;
 
-	of_property_read_u32(np, "snps,phy-addr", &plat->phy_addr);
+	/* Default to phy auto-detection */
+	plat->phy_addr = -1;
+
+	/* "snps,phy-addr" is not a standard property. Mark it as deprecated
+	 * and warn of its use. Remove this when phy node support is added.
+	 */
+	if (of_property_read_u32(np, "snps,phy-addr", &plat->phy_addr) == 0)
+		dev_warn(&pdev->dev, "snps,phy-addr property is deprecated\n");
 
 	plat->mdio_bus_data = devm_kzalloc(&pdev->dev,
 					   sizeof(struct stmmac_mdio_bus_data),