[PATCH 1/2] dt-bindings: mux: gpio-mux: add support for ADG1712

[Antoniu Miclaus <antoniu.miclaus@analog.com>]

Add support for the Analog Devices ADG1712 quad SPST switch to the
existing GPIO multiplexer bindings. The ADG1712 contains four
independent single-pole/single-throw (SPST) switches, each controlled
by a dedicated GPIO pin.

Unlike traditional multiplexers that use GPIOs as binary-encoded
selectors, the ADG1712 treats each GPIO as a direct switch controller.
The mux state represents the combination of all four switches, with
values from 0-15 corresponding to different switch combinations.

For example, state 5 (binary 0101) represents:
- SW1: ON (GPIO0 = 1)
- SW2: OFF (GPIO1 = 0)
- SW3: ON (GPIO2 = 1)
- SW4: OFF (GPIO3 = 0)

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
 .../devicetree/bindings/mux/gpio-mux.yaml     | 24 ++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/mux/gpio-mux.yaml b/Documentation/devicetree/bindings/mux/gpio-mux.yaml
index ef7e33ec85d4..7c5784875683 100644
--- a/Documentation/devicetree/bindings/mux/gpio-mux.yaml
+++ b/Documentation/devicetree/bindings/mux/gpio-mux.yaml
@@ -17,9 +17,14 @@ description: |+
   multiplexer GPIO pins, where the first pin is the least significant
   bit. An active pin is a binary 1, an inactive pin is a binary 0.
 
+  For ADG1712, each GPIO directly controls one independent switch, and
+  the state represents the combination of all four switches (0-15).
+
 properties:
   compatible:
-    const: gpio-mux
+    enum:
+      - gpio-mux
+      - adi,adg1712
 
   mux-gpios:
     description:
@@ -100,4 +105,21 @@ examples:
             };
         };
     };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    // ADG1712 quad SPST switch controller
+    adg1712: switch-controller {
+        compatible = "adi,adg1712";
+        #mux-control-cells = <0>;
+
+        mux-gpios = <&gpio 10 GPIO_ACTIVE_HIGH>,
+                    <&gpio 11 GPIO_ACTIVE_HIGH>,
+                    <&gpio 12 GPIO_ACTIVE_HIGH>,
+                    <&gpio 13 GPIO_ACTIVE_HIGH>;
+
+        // Initial state: SW1=ON, SW2=OFF, SW3=ON, SW4=OFF (binary: 0101 = 5)
+        idle-state = <5>;
+    };
 ...
-- 
2.43.0