dt-bindings: watchdog: Convert stm32 watchdog bindings to json-schema

Convert the STM32 watchdog binding to DT schema format using json-schema
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/watchdog/st,stm32-iwdg.txt

-STM32 Independent WatchDoG (IWDG)
----------------------------------
-
-Required properties:
-- compatible: Should be either:
-  - "st,stm32-iwdg"
-  - "st,stm32mp1-iwdg"
-- reg: Physical base address and length of the registers set for the device
-- clocks: Reference to the clock entry lsi. Additional pclk clock entry
-  is required only for st,stm32mp1-iwdg.
-- clock-names: Name of the clocks used.
-  "lsi" for st,stm32-iwdg
-  "lsi", "pclk" for st,stm32mp1-iwdg
-
-Optional Properties:
-- timeout-sec: Watchdog timeout value in seconds.
-
-Example:
-
-iwdg: watchdog@40003000 {
-	compatible = "st,stm32-iwdg";
-	reg = <0x40003000 0x400>;
-	clocks = <&clk_lsi>;
-	clock-names = "lsi";
-	timeout-sec = <32>;
-};

Documentation/devicetree/bindings/watchdog/st,stm32-iwdg.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/watchdog/st,stm32-iwdg.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics STM32 Independent WatchDoG (IWDG) bindings
+
+maintainers:
+  - Yannick Fertre <yannick.fertre@st.com>
+  - Christophe Roullier <christophe.roullier@st.com>
+
+allOf:
+  - $ref: "watchdog.yaml#"
+
+properties:
+  compatible:
+    enum:
+      - st,stm32-iwdg
+      - st,stm32mp1-iwdg
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Low speed clock
+      - description: Optional peripheral clock
+    minItems: 1
+    maxItems: 2
+
+  clock-names:
+    items:
+      enum:
+        - lsi
+        - pclk
+    minItems: 1
+    maxItems: 2
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+
+examples:
+  - |
+    #include <dt-bindings/clock/stm32mp1-clks.h>
+    watchdog@5a002000 {
+      compatible = "st,stm32mp1-iwdg";
+      reg = <0x5a002000 0x400>;
+      clocks = <&rcc IWDG2>, <&rcc CK_LSI>;
+      clock-names = "pclk", "lsi";
+      timeout-sec = <32>;
+    };
+
+...