dt-bindings: rng: Add Exynos850 support to exynos-trng

The TRNG block in Exynos850 is pretty much the same as in Exynos5250,
but there are two clocks that has to be controlled to make it work:
  1. Functional (operating) clock: called ACLK in Exynos850, the same as
     "secss" clock in Exynos5250
  2. Interface (bus) clock: called PCLK in Exynos850. It has to be
     enabled in order to access TRNG registers

Document Exynos850 compatible and the related clock changes.
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Documentation/devicetree/bindings/rng/samsung,exynos5250-trng.yaml

@@ -12,14 +12,17 @@ maintainers:
 
 properties:
   compatible:
-    const: samsung,exynos5250-trng
+    enum:
+      - samsung,exynos5250-trng
+      - samsung,exynos850-trng
 
   clocks:
-    maxItems: 1
+    minItems: 1
+    maxItems: 2
 
   clock-names:
-    items:
-      - const: secss
+    minItems: 1
+    maxItems: 2
 
   reg:
     maxItems: 1
@@ -30,6 +33,35 @@ required:
   - clock-names
   - reg
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos850-trng
+
+    then:
+      properties:
+        clocks:
+          items:
+            - description: SSS (Security Sub System) operating clock
+            - description: SSS (Security Sub System) bus clock
+
+        clock-names:
+          items:
+            - const: secss
+            - const: pclk
+
+    else:
+      properties:
+        clocks:
+          items:
+            - description: SSS (Security Sub System) operating clock
+
+        clock-names:
+          items:
+            - const: secss
+
 additionalProperties: false
 
 examples: