arm: kirkwood: NSA310S: Use Ethernet PHY name from device tree

In DM Ethernet, the old "egiga0" name is no longer valid, so replace it
with Ethernet PHY name from device tree. Also, Ethernet PHY address
is available so read it from device tree.
Signed-off-by: NTony Dinh <mibodhi@gmail.com>

board/zyxel/nsa310s/nsa310s.c

 // SPDX-License-Identifier: GPL-2.0+
 /*
- * Copyright (C) 2015
- * Gerald Kerma <dreagle@doukki.net>
- * Tony Dinh <mibodhi@gmail.com>
+ * Copyright (C) 2015, 2021 Tony Dinh <mibodhi@gmail.com>
+ * Copyright (C) 2015 Gerald Kerma <dreagle@doukki.net>
  */
 
 #include <common.h>
@@ -81,21 +80,51 @@ int board_init(void)
 	return 0;
 }
 
+static int fdt_get_phy_addr(const char *path)
+{
+	const void *fdt = gd->fdt_blob;
+	const u32 *reg;
+	const u32 *val;
+	int node, phandle, addr;
+
+	/* Find the node by its full path */
+	node = fdt_path_offset(fdt, path);
+	if (node >= 0) {
+		/* Look up phy-handle */
+		val = fdt_getprop(fdt, node, "phy-handle", NULL);
+		if (val) {
+			phandle = fdt32_to_cpu(*val);
+			if (!phandle)
+				return -1;
+			/* Follow it to its node */
+			node = fdt_node_offset_by_phandle(fdt, phandle);
+			if (node) {
+				/* Look up reg */
+				reg = fdt_getprop(fdt, node, "reg", NULL);
+				if (reg) {
+					addr = fdt32_to_cpu(*reg);
+					return addr;
+				}
+			}
+		}
+	}
+	return -1;
+}
+
 #ifdef CONFIG_RESET_PHY_R
 void reset_phy(void)
 {
 	u16 reg;
 	u16 phyaddr;
-	char *name = "egiga0";
+	char *name = "ethernet-controller@72000";
+	char *eth0_path = "/ocp@f1000000/ethernet-controller@72000/ethernet0-port@0";
 
 	if (miiphy_set_current_dev(name))
 		return;
 
-	/* read PHY dev address */
-	if (miiphy_read(name, 0xee, 0xee, (u16 *) &phyaddr)) {
-		printf("could not read PHY dev address\n");
+	phyaddr = fdt_get_phy_addr(eth0_path);
+	if (phyaddr < 0)
 		return;
-	}
 
 	/* set RGMII delay */
 	miiphy_write(name, phyaddr, MV88E1318_PGADR_REG, MV88E1318_MAC_CTRL_PG);
@@ -131,5 +160,7 @@ void reset_phy(void)
 	/* downshift */
 	miiphy_write(name, phyaddr, 0x10, 0x3860);
 	miiphy_write(name, phyaddr, 0x0, 0x9140);
+
+	printf("MV88E1318 PHY initialized on %s\n", name);
 }
 #endif /* CONFIG_RESET_PHY_R */