dt-bindings: display: samsung,exynos7-decon: document iommus, memory-region, and ports

Similar to FIMD and Exynos5433's DECON, the Exynos7 DECON hardware:
- May optionally require an IOMMU to initialize a display region.
- Outputs image data to another block, say an MIC or a DSI master.

If an IOMMU is present, it may also require to access the reserved
framebuffer region.

Document these bindings in the devicetree schema.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

Documentation/devicetree/bindings/display/samsung/samsung,exynos7-decon.yaml

@@ -80,6 +80,21 @@ properties:
       - const: vsync
       - const: lcd_sys
 
+  iommus:
+    maxItems: 1
+
+  memory-region:
+    maxItems: 1
+    description:
+      A phandle to a node describing a reserved framebuffer memory region.
+      For example, the splash memory region set up by the bootloader.
+
+  port:
+    $ref: /schemas/graph.yaml#/properties/port
+    description:
+      Output port which is connected to either a Mobile Image Compressor
+      (MIC) or a DSI Master device.
+
   power-domains:
     maxItems: 1
 
@@ -92,6 +107,7 @@ required:
   - clock-names
   - interrupts
   - interrupt-names
+  - port
   - reg
 
 additionalProperties: false
@@ -118,4 +134,9 @@ examples:
                       "decon0_vclk";
         pinctrl-0 = <&lcd_clk &pwm1_out>;
         pinctrl-names = "default";
+        port {
+            decon_to_dsi: endpoint {
+                remote-endpoint = <&dsi_to_decon>;
+            };
+        };
     };