dt-bindings: clk: fixed-mmio-clock: Convert to YAML

Convert the binding documentatoin for fixed-mmio-clock to YAML.
Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20210903152615.31453-1-kabel@kernel.orgReviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Documentation/devicetree/bindings/clock/fixed-mmio-clock.txt

-Binding for simple memory mapped io fixed-rate clock sources.
-The driver reads a clock frequency value from a single 32-bit memory mapped
-I/O register and registers it as a fixed rate clock.
-
-It was designed for test systems, like FPGA, not for complete, finished SoCs.
-
-This binding uses the common clock binding[1].
-
-[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
-
-Required properties:
-- compatible : shall be "fixed-mmio-clock".
-- #clock-cells : from common clock binding; shall be set to 0.
-- reg : Address and length of the clock value register set.
-
-Optional properties:
-- clock-output-names : From common clock binding.
-
-Example:
-sysclock: sysclock@fd020004 {
-	#clock-cells = <0>;
-	compatible = "fixed-mmio-clock";
-	reg = <0xfd020004 0x4>;
-};

Documentation/devicetree/bindings/clock/fixed-mmio-clock.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/fixed-mmio-clock.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Binding for simple memory mapped IO fixed-rate clock sources
+
+description:
+  This binding describes a fixed-rate clock for which the frequency can
+  be read from a single 32-bit memory mapped I/O register.
+
+  It was designed for test systems, like FPGA, not for complete,
+  finished SoCs.
+
+maintainers:
+  - Jan Kotas <jank@cadence.com>
+
+properties:
+  compatible:
+    const: fixed-mmio-clock
+
+  reg:
+    maxItems: 1
+
+  "#clock-cells":
+    const: 0
+
+  clock-output-names:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - "#clock-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    sysclock: sysclock@fd020004 {
+      compatible = "fixed-mmio-clock";
+      #clock-cells = <0>;
+      reg = <0xfd020004 0x4>;
+      clock-output-names = "sysclk";
+    };
+...