dt-bindings: samsung,mipi-dsim: document exynos7870 DSIM compatible

Add compatible string for Exynos7870 DSIM bridge controller. The
device requires four clock sources, in schema they're named as "bus",
"pll", "byte", and "esc".

Suggested-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml

@@ -24,6 +24,7 @@ properties:
           - samsung,exynos5410-mipi-dsi
           - samsung,exynos5422-mipi-dsi
           - samsung,exynos5433-mipi-dsi
+          - samsung,exynos7870-mipi-dsi
           - fsl,imx8mm-mipi-dsim
           - fsl,imx8mp-mipi-dsim
       - items:
@@ -144,6 +145,32 @@ required:
 
 allOf:
   - $ref: ../dsi-controller.yaml#
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: samsung,exynos7870-mipi-dsi
+
+    then:
+      properties:
+        clocks:
+          minItems: 4
+          maxItems: 4
+
+        clock-names:
+          items:
+            - const: bus
+            - const: pll
+            - const: byte
+            - const: esc
+
+        ports:
+          required:
+            - port@0
+
+      required:
+        - ports
+
   - if:
       properties:
         compatible: