dt-bindings: pinctrl: mt7621: add proper function muxing binding

Not every function can be muxed to a group. Add proper binding which
documents which function can be muxed to a group or set of groups.
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20221231160849.40544-4-arinc.unal@arinc9.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/ralink,mt7621-pinctrl.yaml

@@ -29,21 +29,213 @@ patternProperties:
         $ref: pinmux-node.yaml#
 
         properties:
-          groups:
-            description: The pin group to select.
-            enum: [i2c, jtag, mdio, pcie, rgmii1, rgmii2, sdhci, spi, uart1,
-                   uart2, uart3, wdt]
-
           function:
-            description: The mux function to select.
+            description:
+              A string containing the name of the function to mux to the group.
             enum: [gpio, i2c, i2s, jtag, mdio, nand1, nand2, pcie refclk,
                    pcie rst, pcm, rgmii1, rgmii2, sdhci, spdif2, spdif3, spi,
                    uart1, uart2, uart3, wdt refclk, wdt rst]
 
+          groups:
+            description:
+              An array of strings. Each string contains the name of a group.
+            maxItems: 1
+
         required:
           - groups
           - function
 
+        allOf:
+          - if:
+              properties:
+                function:
+                  const: gpio
+            then:
+              properties:
+                groups:
+                  enum: [i2c, jtag, mdio, pcie, rgmii1, rgmii2, sdhci, spi,
+                         uart1, uart2, uart3, wdt]
+
+          - if:
+              properties:
+                function:
+                  const: i2c
+            then:
+              properties:
+                groups:
+                  enum: [i2c]
+
+          - if:
+              properties:
+                function:
+                  const: i2s
+            then:
+              properties:
+                groups:
+                  enum: [uart3]
+
+          - if:
+              properties:
+                function:
+                  const: jtag
+            then:
+              properties:
+                groups:
+                  enum: [jtag]
+
+          - if:
+              properties:
+                function:
+                  const: mdio
+            then:
+              properties:
+                groups:
+                  enum: [mdio]
+
+          - if:
+              properties:
+                function:
+                  const: nand1
+            then:
+              properties:
+                groups:
+                  enum: [spi]
+
+          - if:
+              properties:
+                function:
+                  const: nand2
+            then:
+              properties:
+                groups:
+                  enum: [sdhci]
+
+          - if:
+              properties:
+                function:
+                  const: pcie refclk
+            then:
+              properties:
+                groups:
+                  enum: [pcie]
+
+          - if:
+              properties:
+                function:
+                  const: pcie rst
+            then:
+              properties:
+                groups:
+                  enum: [pcie]
+
+          - if:
+              properties:
+                function:
+                  const: pcm
+            then:
+              properties:
+                groups:
+                  enum: [uart2]
+
+          - if:
+              properties:
+                function:
+                  const: rgmii1
+            then:
+              properties:
+                groups:
+                  enum: [rgmii1]
+
+          - if:
+              properties:
+                function:
+                  const: rgmii2
+            then:
+              properties:
+                groups:
+                  enum: [rgmii2]
+
+          - if:
+              properties:
+                function:
+                  const: sdhci
+            then:
+              properties:
+                groups:
+                  enum: [sdhci]
+
+          - if:
+              properties:
+                function:
+                  const: spdif2
+            then:
+              properties:
+                groups:
+                  enum: [uart2]
+
+          - if:
+              properties:
+                function:
+                  const: spdif3
+            then:
+              properties:
+                groups:
+                  enum: [uart3]
+
+          - if:
+              properties:
+                function:
+                  const: spi
+            then:
+              properties:
+                groups:
+                  enum: [spi]
+
+          - if:
+              properties:
+                function:
+                  const: uart1
+            then:
+              properties:
+                groups:
+                  enum: [uart1]
+
+          - if:
+              properties:
+                function:
+                  const: uart2
+            then:
+              properties:
+                groups:
+                  enum: [uart2]
+
+          - if:
+              properties:
+                function:
+                  const: uart3
+            then:
+              properties:
+                groups:
+                  enum: [uart3]
+
+          - if:
+              properties:
+                function:
+                  const: wdt refclk
+            then:
+              properties:
+                groups:
+                  enum: [wdt]
+
+          - if:
+              properties:
+                function:
+                  const: wdt rst
+            then:
+              properties:
+                groups:
+                  enum: [wdt]
+
         additionalProperties: false
 
     additionalProperties: false
@@ -57,7 +249,6 @@ required:
 additionalProperties: false
 
 examples:
-  # Pinmux controller node
   - |
     pinctrl {
       compatible = "ralink,mt7621-pinctrl";