dt-bindings: pinctrl: stm32: Support I/O synchronization parameters

Document the support of the I/O synchronization parameters:
- skew-delay-input-ps;
- skew-delay-output-ps;
- st,io-sync.

Forbid 'skew-delay-input-ps' and 'skew-delay-output-ps' to be both
present on the same pin.
Allow the new properties only with compatibles that support them.
Add an example that uses the new properties.

Co-developed-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Signed-off-by: Fabien Dessenne <fabien.dessenne@foss.st.com>
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Author: AntonioBorneo

Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml

@@ -220,12 +220,65 @@ patternProperties:
             minimum: 0
             maximum: 3
 
+          skew-delay-input-ps:
+            description: |
+              IO synchronization skew rate applied to the input path
+            enum: [0, 300, 500, 750, 1000, 1250, 1500, 1750, 2000, 2250, 2500, 2750, 3000, 3250]
+
+          skew-delay-output-ps:
+            description: |
+              IO synchronization latch delay applied to the output path
+            enum: [0, 300, 500, 750, 1000, 1250, 1500, 1750, 2000, 2250, 2500, 2750, 3000, 3250]
+
+          st,io-sync:
+            $ref: /schemas/types.yaml#/definitions/string
+            enum:
+              - pass-through
+              - clock inverted
+              - data on rising edge
+              - data on falling edge
+              - data on both edges
+            description: |
+              IO synchronization through re-sampling or inversion
+              "pass-through"         - data or clock GPIO pass-through
+              "clock inverted"       - clock GPIO inverted
+              "data on rising edge"  - data GPIO re-sampled on clock rising edge
+              "data on falling edge" - data GPIO re-sampled on clock falling edge
+              "data on both edges"   - data GPIO re-sampled on both clock edges
+            default: pass-through
+
         required:
           - pinmux
 
+        # Not allowed both skew-delay-input-ps and skew-delay-output-ps
+        if:
+          required:
+            - skew-delay-input-ps
+        then:
+          properties:
+            skew-delay-output-ps: false
+
 allOf:
   - $ref: pinctrl.yaml#
 
+  - if:
+      not:
+        properties:
+          compatible:
+            contains:
+              enum:
+                - st,stm32mp257-pinctrl
+                - st,stm32mp257-z-pinctrl
+    then:
+      patternProperties:
+        '-[0-9]*$':
+          patternProperties:
+            '^pins':
+              properties:
+                skew-delay-input-ps: false
+                skew-delay-output-ps: false
+                st,io-sync: false
+
 required:
   - compatible
   - '#address-cells'
@@ -306,4 +359,25 @@ examples:
                 pinctrl-names = "default";
     };
 
+  - |
+    #include <dt-bindings/pinctrl/stm32-pinfunc.h>
+    //Example 4 skew-delay and st,io-sync
+      pinctrl: pinctrl@44240000 {
+              compatible = "st,stm32mp257-pinctrl";
+              #address-cells = <1>;
+              #size-cells = <1>;
+              ranges = <0 0x44240000 0xa0400>;
+
+              eth3_rgmii_pins_a: eth3-rgmii-0 {
+                      pins1 {
+                              pinmux = <STM32_PINMUX('A', 6, AF14)>;
+                              st,io-sync = "data on both edges";
+                      };
+                      pins2 {
+                              pinmux = <STM32_PINMUX('H', 2, AF14)>;
+                              skew-delay-output-ps = <500>;
+                      };
+              };
+      };
+
 ...