dt-bindings: timer: armv7m-systick: convert to dtschema

Convert the ARMv7-M system timer bindings to DT schema format.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/1644414747-22159-1-git-send-email-fabrice.gasnier@foss.st.com

Documentation/devicetree/bindings/timer/arm,armv7m-systick.txt

@@ -1,26 +0,0 @@
-* ARMv7M System Timer
-
-ARMv7-M includes a system timer, known as SysTick. Current driver only
-implements the clocksource feature.
-
-Required properties:
-- compatible	  : Should be "arm,armv7m-systick"
-- reg		  : The address range of the timer
-
-Required clocking property, have to be one of:
-- clocks	  : The input clock of the timer
-- clock-frequency : The rate in HZ in input of the ARM SysTick
-
-Examples:
-
-systick: timer@e000e010 {
-	compatible = "arm,armv7m-systick";
-	reg = <0xe000e010 0x10>;
-	clocks = <&clk_systick>;
-};
-
-systick: timer@e000e010 {
-	compatible = "arm,armv7m-systick";
-	reg = <0xe000e010 0x10>;
-	clock-frequency = <90000000>;
-};

Documentation/devicetree/bindings/timer/arm,armv7m-systick.yaml

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/arm,armv7m-systick.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARMv7M System Timer
+
+maintainers:
+  - Alexandre Torgue <alexandre.torgue@foss.st.com>
+  - Fabrice Gasnier <fabrice.gasnier@foss.st.com>
+
+description: ARMv7-M includes a system timer, known as SysTick.
+
+properties:
+  compatible:
+    const: arm,armv7m-systick
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-frequency: true
+
+oneOf:
+  - required:
+      - clocks
+  - required:
+      - clock-frequency
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    timer@e000e010 {
+        compatible = "arm,armv7m-systick";
+        reg = <0xe000e010 0x10>;
+        clocks = <&clk_systick>;
+    };
+
+  - |
+    timer@e000e010 {
+        compatible = "arm,armv7m-systick";
+        reg = <0xe000e010 0x10>;
+        clock-frequency = <90000000>;
+    };
+
+...