lantiq: xrx200: handle EPROBE_DEFER for MAC address

The xrx200 ethernet driver falls back to a random MAC address on any
error from of_get_ethdev_address(), including -EPROBE_DEFER. When the
MAC address comes from an nvmem layout driver (such as u-boot-env on
NAND), the nvmem cell may not be available yet at first probe attempt.

Fix this by propagating EPROBE_DEFER so the driver probe is deferred
until the nvmem cell becomes available.

Tested on Zyxel P-2812HNU-F1 (NAND, u-boot-env nvmem layout).

Signed-off-by: Burak Aydos <byhexadecimal@gmail.com>
Link: openwrt/openwrt#21861
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

Author: bYHexadecimal

target/linux/lantiq/patches-6.12/0801-net-ethernet-lantiq-xrx200-handle-EPROBE_DEFER-for-MAC-address.patch

@@ -0,0 +1,30 @@
+From: Burak Aydos <byhexadecimal@gmail.com>
+Date: Mon, 03 Feb 2026 12:00:00 +0300
+Subject: [PATCH] net: ethernet: lantiq: xrx200: handle EPROBE_DEFER for MAC
+ address
+
+When the MAC address is provided by an nvmem layout driver (such as
+u-boot-env), the nvmem cell may not be available yet when the ethernet
+driver probes. In this case, of_get_ethdev_address() returns
+-EPROBE_DEFER to indicate the driver should be retried later.
+
+Currently the driver treats all errors equally and falls back to a
+random MAC address. Fix this by propagating EPROBE_DEFER so the
+driver probe is deferred until the nvmem cell becomes available.
+
+Signed-off-by: Burak Aydos <byhexadecimal@gmail.com>
+---
+ drivers/net/ethernet/lantiq_xrx200.c | 2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/drivers/net/ethernet/lantiq_xrx200.c
++++ b/drivers/net/ethernet/lantiq_xrx200.c
+@@ -597,6 +597,8 @@ static int xrx200_probe(struct platform_
+ 	}
+ 
+ 	err = of_get_ethdev_address(np, net_dev);
++	if (err == -EPROBE_DEFER)
++		return err;
+ 	if (err)
+ 		eth_hw_addr_random(net_dev);
+