dt-bindings: serial: samsung: add exynos7870-uart compatible

Document the compatible string for Exynos7870's UART driver. The
devicetree property samsung,uart-fifosize must be mandatory, as the
driver enquires about the FIFO sizes. This feature makes it compatible
with Exynos8895's UART.

Signed-off-by: Kaustabh Chakraborty <[email protected]>
Reviewed-by: Krzysztof Kozlowski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Kaustabh Chakraborty

Documentation/devicetree/bindings/serial/samsung_uart.yaml

@@ -42,6 +42,10 @@ properties:
               - samsung,exynosautov9-uart
               - samsung,exynosautov920-uart
           - const: samsung,exynos850-uart
+      - items:
+          - enum:
+              - samsung,exynos7870-uart
+          - const: samsung,exynos8895-uart
 
   reg:
     maxItems: 1