[openwrt/openwrt] realtek: hog the GS1900-24E external IC reset line

[LEDE Commits]

svanheule pushed a commit to openwrt/openwrt.git, branch openwrt-25.12:
https://git.openwrt.org/cdc92ce56099f938ca936f33990a4e65e77c828e

commit cdc92ce56099f938ca936f33990a4e65e77c828e
Author: Sander Vanheule <sander at svanheule.net>
AuthorDate: Sat Feb 21 15:00:39 2026 +0100

    realtek: hog the GS1900-24E external IC reset line
    
    The GPIO line connecting to the reset signals of the GS1900-24E(A1)'s
    external ICs (RTL8218B phys and RTL8231 expander) cannot be asserted by
    the MDIO subsystem, as the reset is shared between busses.
    
    To prevent users from accidentally asserting the reset line, a GPIO hog
    is created to permanently de-assert the signal, reliably keeping the
    phys and GPIO expanders on.
    
    Tested-by: Simon Fischer <simi.fischa at gmail.com>
    Signed-off-by: Sander Vanheule <sander at svanheule.net>
    (cherry picked from commit ba57225066243b28d2802ea5c47313c97767150e)
---
 target/linux/realtek/dts/rtl8382_zyxel_gs1900-24e-a1.dts | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/target/linux/realtek/dts/rtl8382_zyxel_gs1900-24e-a1.dts b/target/linux/realtek/dts/rtl8382_zyxel_gs1900-24e-a1.dts
index c54648cc32..4cffc040ed 100644
--- a/target/linux/realtek/dts/rtl8382_zyxel_gs1900-24e-a1.dts
+++ b/target/linux/realtek/dts/rtl8382_zyxel_gs1900-24e-a1.dts
@@ -8,6 +8,16 @@
 	model = "Zyxel GS1900-24E A1";
 };
 
+&gpio0 {
+	/* Shared between the main and aux MDIO busses */
+	mdio_reset {
+		gpio-hog;
+		gpios = <1 GPIO_ACTIVE_LOW>;
+		output-low;
+		line-name = "mdio-reset";
+	};
+};
+
 &mdio_bus0 {
 	EXTERNAL_PHY(0)
 	EXTERNAL_PHY(1)