dt-bindings: mtd: Add Loongson-1 NAND Controller

Add devicetree binding document for Loongson-1 NAND controller.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Keguang Zhang <keguang.zhang@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

Documentation/devicetree/bindings/mtd/loongson,ls1b-nand-controller.yaml

@@ -0,0 +1,72 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mtd/loongson,ls1b-nand-controller.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson-1 NAND Controller
+
+maintainers:
+  - Keguang Zhang <keguang.zhang@gmail.com>
+
+description:
+  The Loongson-1 NAND controller abstracts all supported operations,
+  meaning it does not support low-level access to raw NAND flash chips.
+  Moreover, the controller is paired with the DMA engine to perform
+  READ and PROGRAM functions.
+
+allOf:
+  - $ref: nand-controller.yaml
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - loongson,ls1b-nand-controller
+          - loongson,ls1c-nand-controller
+      - items:
+          - enum:
+              - loongson,ls1a-nand-controller
+          - const: loongson,ls1b-nand-controller
+
+  reg:
+    maxItems: 2
+
+  reg-names:
+    items:
+      - const: nand
+      - const: nand-dma
+
+  dmas:
+    maxItems: 1
+
+  dma-names:
+    const: rxtx
+
+required:
+  - compatible
+  - reg
+  - reg-names
+  - dmas
+  - dma-names
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    nand-controller@1fe78000 {
+        compatible = "loongson,ls1b-nand-controller";
+        reg = <0x1fe78000 0x24>, <0x1fe78040 0x4>;
+        reg-names = "nand", "nand-dma";
+        dmas = <&dma 0>;
+        dma-names = "rxtx";
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        nand@0 {
+            reg = <0>;
+            label = "ls1x-nand";
+            nand-use-soft-ecc-engine;
+            nand-ecc-algo = "hamming";
+        };
+    };