dt-bindings: watchdog: Document Exynos850 watchdog bindings

Exynos850 SoC has two CPU clusters:
  - cluster 0: contains CPUs #0, #1, #2, #3
  - cluster 1: contains CPUs #4, #5, #6, #7

Each cluster has its own dedicated watchdog timer. Those WDT instances
are controlled using different bits in PMU registers, new
"samsung,index" property is added to tell the driver which bits to use
for defined watchdog node.

Also on Exynos850 the peripheral clock and the source clock are two
different clocks. Provide a way to specify two clocks in watchdog device
tree node.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20211107202943.8859-3-semen.protsenko@linaro.org
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Documentation/devicetree/bindings/watchdog/samsung-wdt.yaml

@@ -22,25 +22,32 @@ properties:
       - samsung,exynos5250-wdt                # for Exynos5250
       - samsung,exynos5420-wdt                # for Exynos5420
       - samsung,exynos7-wdt                   # for Exynos7
+      - samsung,exynos850-wdt                 # for Exynos850
 
   reg:
     maxItems: 1
 
   clocks:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   clock-names:
-    items:
-      - const: watchdog
+    minItems: 1
+    maxItems: 2
 
   interrupts:
     maxItems: 1
 
+  samsung,cluster-index:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Index of CPU cluster on which watchdog is running (in case of Exynos850)
+
   samsung,syscon-phandle:
     $ref: /schemas/types.yaml#/definitions/phandle
     description:
       Phandle to the PMU system controller node (in case of Exynos5250,
-      Exynos5420 and Exynos7).
+      Exynos5420, Exynos7 and Exynos850).
 
 required:
   - compatible
@@ -59,9 +66,39 @@ allOf:
               - samsung,exynos5250-wdt
               - samsung,exynos5420-wdt
               - samsung,exynos7-wdt
+              - samsung,exynos850-wdt
     then:
       required:
         - samsung,syscon-phandle
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - samsung,exynos850-wdt
+    then:
+      properties:
+        clocks:
+          items:
+            - description: Bus clock, used for register interface
+            - description: Source clock (driving watchdog counter)
+        clock-names:
+          items:
+            - const: watchdog
+            - const: watchdog_src
+        samsung,cluster-index:
+          enum: [0, 1]
+      required:
+        - samsung,cluster-index
+    else:
+      properties:
+        clocks:
+          items:
+            - description: Bus clock, which is also a source clock
+        clock-names:
+          items:
+            - const: watchdog
+        samsung,cluster-index: false
 
 unevaluatedProperties: false