devicetree: serial: Document msm_serial bindings

Let's fix up the msm serial device bindings so that it's clearer
what hardware is supported. Instead of using hsuart (for high
speed uart) let's use uartdm because that matches the actual name
of the hardware. Also, let's add the version information in case
we need to differentiate between different versions of the
hardware in the future. Finally, lets specify that clocks are
required (the clock bindings didn't exist when the original
binding was written) and also specify dma bindings just in case
we want to use it in software. We split the binding into two
files to make it clearer what's required and not required.

Cc: David Brown <davidb@codeaurora.org>
Cc: <devicetree@vger.kernel.org>
Acked-by: Kumar Gala <galak@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/qcom,msm-uart.txt

@@ -0,0 +1,25 @@
+* MSM Serial UART
+
+The MSM serial UART hardware is designed for low-speed use cases where a
+dma-engine isn't needed. From a software perspective it's mostly compatible
+with the MSM serial UARTDM except that it only supports reading and writing one
+character at a time.
+
+Required properties:
+- compatible: Should contain "qcom,msm-uart"
+- reg: Should contain UART register location and length.
+- interrupts: Should contain UART interrupt.
+- clocks: Should contain the core clock.
+- clock-names: Should be "core".
+
+Example:
+
+A uart device at 0xa9c00000 with interrupt 11.
+
+serial@a9c00000 {
+	compatible = "qcom,msm-uart";
+	reg = <0xa9c00000 0x1000>;
+	interrupts = <11>;
+	clocks = <&uart_cxc>;
+	clock-names = "core";
+};

Documentation/devicetree/bindings/serial/qcom,msm-uartdm.txt

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+* MSM Serial UARTDM
+
+The MSM serial UARTDM hardware is designed for high-speed use cases where the
+transmit and/or receive channels can be offloaded to a dma-engine. From a
+software perspective it's mostly compatible with the MSM serial UART except
+that it supports reading and writing multiple characters at a time.
+
+Required properties:
+- compatible: Should contain at least "qcom,msm-uartdm".
+              A more specific property should be specified as follows depending
+	      on the version:
+		"qcom,msm-uartdm-v1.1"
+		"qcom,msm-uartdm-v1.2"
+		"qcom,msm-uartdm-v1.3"
+		"qcom,msm-uartdm-v1.4"
+- reg: Should contain UART register locations and lengths. The first
+       register shall specify the main control registers. An optional second
+       register location shall specify the GSBI control region.
+       "qcom,msm-uartdm-v1.3" is the only compatible value that might
+       need the GSBI control region.
+- interrupts: Should contain UART interrupt.
+- clocks: Should contain the core clock and the AHB clock.
+- clock-names: Should be "core" for the core clock and "iface" for the
+	       AHB clock.
+
+Optional properties:
+- dmas: Should contain dma specifiers for transmit and receive channels
+- dma-names: Should contain "tx" for transmit and "rx" for receive channels
+
+Examples:
+
+A uartdm v1.4 device with dma capabilities.
+
+serial@f991e000 {
+	compatible = "qcom,msm-uartdm-v1.4", "qcom,msm-uartdm";
+	reg = <0xf991e000 0x1000>;
+	interrupts = <0 108 0x0>;
+	clocks = <&blsp1_uart2_apps_cxc>, <&blsp1_ahb_cxc>;
+	clock-names = "core", "iface";
+	dmas = <&dma0 0>, <&dma0 1>;
+	dma-names = "tx", "rx";
+};
+
+A uartdm v1.3 device without dma capabilities and part of a GSBI complex.
+
+serial@19c40000 {
+	compatible = "qcom,msm-uartdm-v1.3", "qcom,msm-uartdm";
+	reg = <0x19c40000 0x1000>,
+	      <0x19c00000 0x1000>;
+	interrupts = <0 195 0x0>;
+	clocks = <&gsbi5_uart_cxc>, <&gsbi5_ahb_cxc>;
+	clock-names = "core", "iface";
+};