dt-bindings: mips: Add gardena vendor prefix and board description

This patch adds the vendor prefix for gardena and a short description
including the compatible string for the "GARDENA smart Gateway" based
on the MT7688 SoC.

Signed-off-by: Stefan Roese <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Paul Burton <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]

Documentation/devicetree/bindings/mips/ralink.txt

···
   ralink,mt7620n-soc
   ralink,mt7628a-soc
   ralink,mt7688a-soc
+
+2. Boards
+
+GARDENA smart Gateway (MT7688)
+
+This board is based on the MediaTek MT7688 and equipped with 128 MiB
+of DDR and 8 MiB of flash (SPI NOR) and additional 128MiB SPI NAND
+storage.
+
+------------------------------
+Required root node properties:
+- compatible = "gardena,smart-gateway-mt7688", "ralink,mt7688a-soc",
+		"ralink,mt7628a-soc";

Documentation/devicetree/bindings/vendor-prefixes.yaml

···
     description: Freescale Semiconductor
   "^fujitsu,.*":
     description: Fujitsu Ltd.
+  "^gardena,.*":
+    description: GARDENA GmbH
   "^gateworks,.*":
     description: Gateworks Corporation
   "^gcw,.*":