Documentation: cs40l2x: Extend support for CS40L2X family

Added device tree binding documentation for CS40L25, CS40L25A and
CS40L25B devices.

Change-Id: I4b809d34aad193915f25044ade404db83d6aa3ad
Signed-off-by: Jeff LaBundy <jeff.labundy@cirrus.com>
Signed-off-by: Ravi Vembu <raviv@motorola.com>

Documentation/devicetree/bindings/cs40l2x.txt

@@ -0,0 +1,46 @@
+CS40L20 Boosted Haptics Driver
+
+Required properties:
+
+  - compatible : One of "cirrus,cs40l20", "cirrus,cs40l25", "cirrus,cs40l25a"
+    or "cirrus,cs40l25b".
+
+  - reg : The I2C slave address of the device.
+
+  - VA-supply, VP-supply : Regulators for the device's VA and VP supplies,
+    respectively. See the following:
+    Documentation/devicetree/bindings/regulator/regulator.txt
+
+  - cirrus,boost-ind-nanohenry : Boost inductor value, expressed in nH. Valid
+    values include 1000, 1200, 1500 and 2200.
+
+  - cirrus,boost-cap-microfarad : Total equivalent boost capacitance on the VBST
+    and VAMP pins, derated at 11 volts DC. The value must be rounded to the
+    nearest integer and expressed in uF.
+
+  - cirrus,boost-ipk-milliamp : Boost inductor peak current, expressed in mA.
+    Valid values range from 1600 to 4500 (inclusive) in steps of 50.
+
+Optional properties:
+
+  - reset-gpios : GPIO used for resetting the device.
+
+  - cirrus,refclk-gpio2 : Boolean for configuring the device to expect its
+    32.768-kHz reference clock on the REFCLK/GPIO2 pin. If this property is
+    omitted, the device expects its 32.768-kHz reference clock on the
+    ASP_BCLK/REFCLK pin. This property is ignored for CS40L25A and CS40L25B
+    devices as reference clock selection is configured automatically.
+
+Example:
+
+  cs40l20: cs40l20@43 {
+    compatible = "cirrus,cs40l20";
+    reg = <0x43>;
+    reset-gpios = <&gpio0 54 0>;
+    VA-supply = <&dummy_vreg>;
+    VP-supply = <&dummy_vreg>;
+    cirrus,boost-ind-nanohenry = <1000>;
+    cirrus,boost-cap-microfarad = <4>;
+    cirrus,boost-ipk-milliamp = <4500>;
+    cirrus,refclk-gpio2;
+  };