dt-bindings: i3c: Convert cdns,i3c-master to DT schema

Convert the Cadence I3C master to DT schema format. This fixes a warning
as it is used in the i3c.yaml example.

The "nintendo,nunchuk" is not documented by a schema, so change the
example child device to something which is documented.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220422192224.2594098-1-robh@kernel.org

Documentation/devicetree/bindings/i3c/cdns,i3c-master.yaml

@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/i3c/cdns,i3c-master.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Cadence I3C master block
+
+maintainers:
+  - Boris Brezillon <bbrezillon@kernel.org>
+
+allOf:
+  - $ref: i3c.yaml#
+
+properties:
+  compatible:
+    const: cdns,i3c-master
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 2
+
+  clock-names:
+    items:
+      - const: pclk
+      - const: sysclk
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i3c-master@d040000 {
+        compatible = "cdns,i3c-master";
+        clocks = <&coreclock>, <&i3csysclock>;
+        clock-names = "pclk", "sysclk";
+        interrupts = <3 0>;
+        reg = <0x0d040000 0x1000>;
+        #address-cells = <3>;
+        #size-cells = <0>;
+        i2c-scl-hz = <100000>;
+
+        eeprom@57{
+            compatible = "atmel,24c01";
+            reg = <0x57 0x0 0x10>;
+            pagesize = <0x8>;
+        };
+    };
+...