spi: dt-bindings: add SpacemiT K1 SPI support

Add support for the SPI controller implemented by the SpacemiT K1 SoC.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Alex Elder <elder@riscstar.com>
Signed-off-by: Guodong Xu <guodong@riscstar.com>
Link: https://patch.msgid.link/20260502-spi-spacemit-k1-v10-1-f412e1ae8a34@riscstar.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/spacemit,k1-spi.yaml

@@ -0,0 +1,84 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spi/spacemit,k1-spi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SpacemiT K1 SoC Serial Peripheral Interface (SPI)
+
+maintainers:
+  - Alex Elder <elder@kernel.org>
+
+description:
+  The SpacemiT K1 SoC implements a SPI controller that has two 32-entry
+  FIFOs, for transmit and receive.  Details are currently available in
+  section 18.2.1 of the K1 User Manual, found in the SpacemiT Keystone
+  K1 Documentation[1].  The controller transfers words using PIO.  DMA
+  transfers are supported as well, if both TX and RX DMA channels are
+  specified,
+
+  [1] https://developer.spacemit.com/documentation
+
+allOf:
+  - $ref: /schemas/spi/spi-controller.yaml#
+
+properties:
+  compatible:
+    const: spacemit,k1-spi
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    items:
+      - description: Core clock
+      - description: Bus clock
+
+  clock-names:
+    items:
+      - const: core
+      - const: bus
+
+  resets:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  dmas:
+    items:
+      - description: RX DMA channel
+      - description: TX DMA channel
+
+  dma-names:
+    items:
+      - const: rx
+      - const: tx
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - clock-names
+  - resets
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+
+    #include <dt-bindings/clock/spacemit,k1-syscon.h>
+    spi@d401c000 {
+        compatible = "spacemit,k1-spi";
+        reg = <0xd401c000 0x30>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+        clocks = <&syscon_apbc CLK_SSP3>,
+                 <&syscon_apbc CLK_SSP3_BUS>;
+        clock-names = "core", "bus";
+        resets = <&syscon_apbc RESET_SSP3>;
+        interrupts = <55>;
+        dmas = <&pdma 20>, <&pdma 19>;
+        dma-names = "rx", "tx";
+    };