dt-bindings: mmc: Document the Amlogic Meson SDHC MMC host controller

This documents the devicetree bindings for the SDHC MMC host controller
found in Meson6, Meson8, Meson8b and Meson8m2 SoCs. It can use a
bus-width of 1/4/8-bit and it supports eMMC spec 4.4x/4.5x including
HS200 mode (up to 100MHz clock). It embeds an internal clock controller
which outputs four clocks (mod_clk, sd_clk, tx_clk and rx_clk) and is
fed by four external input clocks (clkin[0-3]). "pclk" is the module
register clock, it has to be enabled to access the registers.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200512204147.504087-2-martin.blumenstingl@googlemail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdhc.yaml b/Documentation/devicetree/bindings/mmc/amlogic,meson-mx-sdhc.yaml
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+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mmc/amlogic,meson-mx-sdhc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Amlogic Meson SDHC controller Device Tree Bindings
+
+allOf:
+  - $ref: "mmc-controller.yaml"
+
+maintainers:
+  - Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+
+description: |
+  The SDHC MMC host controller on Amlogic SoCs provides an eMMC and MMC
+  card interface with 1/4/8-bit bus width.
+  It supports eMMC spec 4.4x/4.5x including HS200 (up to 100MHz clock).
+
+properties:
+  compatible:
+    items:
+      - enum:
+        - amlogic,meson8-sdhc
+        - amlogic,meson8b-sdhc
+        - amlogic,meson8m2-sdhc
+      - const: amlogic,meson-mx-sdhc
+
+  reg:
+    minItems: 1
+
+  interrupts:
+    minItems: 1
+
+  clocks:
+    minItems: 5
+
+  clock-names:
+    items:
+      - const: clkin0
+      - const: clkin1
+      - const: clkin2
+      - const: clkin3
+      - const: pclk
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    sdhc: mmc@8e00 {
+      compatible = "amlogic,meson8-sdhc", "amlogic,meson-mx-sdhc";
+      reg = <0x8e00 0x42>;
+      interrupts = <GIC_SPI 78 IRQ_TYPE_EDGE_RISING>;
+      clocks = <&xtal>,
+               <&fclk_div4>,
+               <&fclk_div3>,
+               <&fclk_div5>,
+               <&sdhc_pclk>;
+      clock-names = "clkin0", "clkin1", "clkin2", "clkin3", "pclk";
+    };