Implement ndo_get_phys_port_id() and ndo_get_phys_port_name() callbacks
for the Renesas RZ/G3E GBETH driver.

The port ID is an 8-byte identifier constructed from:
- Permanent MAC address if available (addr_assign_type == NET_ADDR_PERM)
- Renesas OUI (74:90:50) as fallback for random/generated MACs
- Port index from 'port-id' DT property or ethernet alias

The port name resolution follows this hierarchy:
- 'port-name' DT property if specified (allows custom names like "mgmt")
- "p<N>" format using 'port-id' DT property
- "p<N>" format using ethernet alias index as fallback

Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
---
 .../stmicro/stmmac/dwmac-renesas-gbeth.c      | 56 +++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-renesas-gbeth.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-renesas-gbeth.c
index bc7bb975803ca..5acb65b0e4f06 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-renesas-gbeth.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-renesas-gbeth.c
@@ -16,7 +16,9 @@
 #include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/module.h>
+#include <linux/netdevice.h>
 #include <linux/of.h>
+#include <linux/of_net.h>
 #include <linux/pcs-rzn1-miic.h>
 #include <linux/platform_device.h>
 #include <linux/reset.h>
@@ -91,6 +93,57 @@ static struct phylink_pcs *renesas_gmac_select_pcs(struct stmmac_priv *priv,
 	return priv->hw->phylink_pcs;
 }
 
+static int renesas_gbeth_get_port_id(struct device *dev)
+{
+	int port_id;
+
+	if (!device_property_read_u32(dev, "renesas,port-id", &port_id))
+		return port_id;
+
+	port_id = of_alias_get_id(dev_of_node(dev), "ethernet");
+
+	return port_id < 0 ? 0 : port_id;
+}
+
+static int renesas_gbeth_get_phys_port_name(struct net_device *ndev,
+					    char *name, size_t len)
+{
+	struct stmmac_priv *priv = netdev_priv(ndev);
+	struct renesas_gbeth *gbeth = priv->plat->bsp_priv;
+	const char *port_name;
+
+	if (!device_property_read_string(gbeth->dev, "renesas,port-name", &port_name))
+		return snprintf(name, len, "%s", port_name) >= len ? -EINVAL : 0;
+
+	return snprintf(name, len, "p%d", renesas_gbeth_get_port_id(gbeth->dev)) >= len ? -EINVAL : 0;
+}
+
+static int renesas_gbeth_get_phys_port_id(struct net_device *ndev,
+					  struct netdev_phys_item_id *ppid)
+{
+	struct stmmac_priv *priv = netdev_priv(ndev);
+	struct renesas_gbeth *gbeth = priv->plat->bsp_priv;
+	u8 *id = ppid->id;
+
+	if (ndev->addr_assign_type == NET_ADDR_PERM) {
+		memcpy(id, ndev->perm_addr, ETH_ALEN);
+	} else {
+		/* Fallback: Renesas OUI prefix (74:90:50) */
+		id[0] = 0x74;
+		id[1] = 0x90;
+		id[2] = 0x50;
+		id[3] = 0x00;
+		id[4] = 0x00;
+		id[5] = 0x00;
+	}
+
+	id[6] = renesas_gbeth_get_port_id(gbeth->dev) & 0xff;
+	id[7] = 0x00;
+	ppid->id_len = 8;
+
+	return 0;
+}
+
 static int renesas_gbeth_init(struct platform_device *pdev, void *priv)
 {
 	struct plat_stmmacenet_data *plat_dat;
@@ -194,6 +247,9 @@ static int renesas_gbeth_probe(struct platform_device *pdev)
 		plat_dat->select_pcs = renesas_gmac_select_pcs;
 	}
 
+	plat_dat->get_phys_port_id = renesas_gbeth_get_phys_port_id;
+	plat_dat->get_phys_port_name = renesas_gbeth_get_phys_port_name;
+
 	return devm_stmmac_pltfr_probe(pdev, plat_dat, &stmmac_res);
 }
 
-- 
2.25.1