dt-bindings: mux: Document mux-states property

In some cases, it is required to provide the state to which the mux
controller has to be set to, from the consumer device tree node. Document
the property mux-states that can be used for adding this support.

Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/f4d02ac8-23ee-d891-4056-75c672cc59c9@axentia.se
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/mux/mux-controller.yaml

@@ -25,7 +25,9 @@ description: |
   --------------------
 
   Mux controller nodes must specify the number of cells used for the
-  specifier using the '#mux-control-cells' property.
+  specifier using the '#mux-control-cells' or '#mux-state-cells' property.
+  The value of '#mux-state-cells' will always be one greater than the value
+  of '#mux-control-cells'.
 
   Optionally, mux controller nodes can also specify the state the mux should
   have when it is idle. The idle-state property is used for this. If the
@@ -67,6 +69,8 @@ select:
           pattern: '^mux-controller'
     - required:
         - '#mux-control-cells'
+    - required:
+        - '#mux-state-cells'
 
 properties:
   $nodename:
@@ -75,6 +79,9 @@ properties:
   '#mux-control-cells':
     enum: [ 0, 1 ]
 
+  '#mux-state-cells':
+    enum: [ 1, 2 ]
+
   idle-state:
     $ref: /schemas/types.yaml#/definitions/int32
     minimum: -2
@@ -179,4 +186,21 @@ examples:
             };
         };
     };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    mux1: mux-controller {
+        compatible = "gpio-mux";
+        #mux-state-cells = <1>;
+        mux-gpios = <&exp_som 2 GPIO_ACTIVE_HIGH>;
+    };
+
+    transceiver4: can-phy4 {
+        compatible = "ti,tcan1042";
+        #phy-cells = <0>;
+        max-bitrate = <5000000>;
+        standby-gpios = <&exp_som 7 GPIO_ACTIVE_HIGH>;
+        mux-states = <&mux1 1>;
+    };
 ...