dt-bindings: mmc: arasan: Document 'xlnx,zynqmp-8.9a' controller

Add documentation for 'xlnx,zynqmp-8.9a' SDHCI controller and optional
properties followed by example.

Signed-off-by: Manish Narani <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Ulf Hansson <[e-mail]>

Documentation/devicetree/bindings/mmc/arasan,sdhci.txt

···
     - "arasan,sdhci-5.1": generic Arasan SDHCI 5.1 PHY
     - "rockchip,rk3399-sdhci-5.1", "arasan,sdhci-5.1": rk3399 eMMC PHY
       For this device it is strongly suggested to include arasan,soc-ctl-syscon.
+    - "xlnx,zynqmp-8.9a": ZynqMP SDHCI 8.9a PHY
+      For this device it is strongly suggested to include clock-output-names and
+      #clock-cells.
     - "ti,am654-sdhci-5.1", "arasan,sdhci-5.1": TI AM654 MMC PHY
 	Note: This binding has been deprecated and moved to [5].
     - "intel,lgm-sdhci-5.1-emmc", "arasan,sdhci-5.1": Intel LGM eMMC PHY
···
     properly. Test mode can be used to force the controller to function.
   - xlnx,int-clock-stable-broken: when present, the controller always reports
     that the internal clock is stable even when it is not.
+
+  - xlnx,mio-bank: When specified, this will indicate the MIO bank number in
+    which the command and data lines are configured. If not specified, driver
+    will assume this as 0.
 
 Example:
 	sdhci@e0100000 {
···
 		phys = <&emmc_phy>;
 		phy-names = "phy_arasan";
 		#clock-cells = <0>;
+	};
+
+	sdhci: mmc@ff160000 {
+		compatible = "xlnx,zynqmp-8.9a", "arasan,sdhci-8.9a";
+		interrupt-parent = <&gic>;
+		interrupts = <0 48 4>;
+		reg = <0x0 0xff160000 0x0 0x1000>;
+		clocks = <&clk200>, <&clk200>;
+		clock-names = "clk_xin", "clk_ahb";
+		clock-output-names = "clk_out_sd0", "clk_in_sd0";
+		#clock-cells = <1>;
+		clk-phase-sd-hs = <63>, <72>;
 	};
 
 	emmc: sdhci@ec700000 {