dt-bindings: watchdog: samsung-wdt: Split if:then: and constrain more

Binding defined two if:then: blocks covering different conditions but
not fully constraining the properties per each variant:
1. "if:" to require samsung,syscon-phandle,
2. "if:" with "else:" to narrow number of clocks and require or disallow
   samsung,cluster-index.

This still did not cover following cases:
1. Disallow samsung,syscon-phandle when not applicable,
2. Narrow samsung,cluster-index to [0, 1], for SoCs with only two
   clusters.

Solving this in current format would lead to spaghetti code, so re-write
entire "if:then:" approach into mutually exclusive cases so each SoC
appears only in one "if:" block.  This allows to forbid
samsung,syscon-phandle for S3C6410, and narrow samsung,cluster-index
to [0, 1].

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

Author: krzk

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

@@ -74,26 +74,31 @@ allOf:
           contains:
             enum:
               - google,gs101-wdt
-              - samsung,exynos5250-wdt
-              - samsung,exynos5420-wdt
-              - samsung,exynos7-wdt
               - samsung,exynos850-wdt
-              - samsung,exynos990-wdt
               - samsung,exynosautov9-wdt
               - samsung,exynosautov920-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
         - samsung,syscon-phandle
+
   - if:
       properties:
         compatible:
           contains:
             enum:
-              - google,gs101-wdt
-              - samsung,exynos850-wdt
               - samsung,exynos990-wdt
-              - samsung,exynosautov9-wdt
-              - samsung,exynosautov920-wdt
     then:
       properties:
         clocks:
@@ -106,7 +111,35 @@ allOf:
             - const: watchdog_src
       required:
         - samsung,cluster-index
-    else:
+        - samsung,syscon-phandle
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - samsung,exynos5250-wdt
+              - samsung,exynos5420-wdt
+              - samsung,exynos7-wdt
+    then:
+      properties:
+        clocks:
+          items:
+            - description: Bus clock, which is also a source clock
+        clock-names:
+          items:
+            - const: watchdog
+        samsung,cluster-index: false
+      required:
+        - samsung,syscon-phandle
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - samsung,s3c6410-wdt
+    then:
       properties:
         clocks:
           items:
@@ -115,6 +148,7 @@ allOf:
           items:
             - const: watchdog
         samsung,cluster-index: false
+        samsung,syscon-phandle: false
 
 unevaluatedProperties: false