[PATCH 3/4] doc: dt: pwm: add binding for ChromeOS EC PWM

[Brian Norris <briannorris@chromium.org>]

The ChromeOS Embedded Controller can support controlling its attached
PWMs via its host-command interface. The number of supported PWMs varies
on a per-board basis, so we define a "google,max-pwms" property to
handle this. And because the EC only allows specifying the duty cycle
and not the period, we don't specify the period via pwm-cells, and
instead have only support 1 cell -- to specify the index.

Signed-off-by: Brian Norris <briannorris@chromium.org>
---
 .../devicetree/bindings/pwm/google,cros-ec-pwm.txt | 25 ++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/google,cros-ec-pwm.txt

diff --git a/Documentation/devicetree/bindings/pwm/google,cros-ec-pwm.txt b/Documentation/devicetree/bindings/pwm/google,cros-ec-pwm.txt
new file mode 100644
index 000000000000..f1c9540fc23f
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/google,cros-ec-pwm.txt
@@ -0,0 +1,25 @@
+* PWM controlled by ChromeOS EC
+
+Google's ChromeOS EC PWM is a simple PWM attached to the Embedded Controller
+(EC) and controlled via a host-command interface.
+
+An EC PWM node should be only found as a sub-node of the EC node (see
+Documentation/devicetree/bindings/mfd/cros-ec.txt).
+
+Required properties:
+- compatible: Must contain "google,cros-ec-pwm"
+- #pwm-cells: Should be 1. The cell specifies the PWM index.
+- google,max-pwms: Specifies the number of PWMs supported by the EC.
+
+Example:
+	cros-ec@0 {
+		compatible = "google,cros-ec-spi";
+
+		...
+
+		cros_ec_pwm: ec-pwm {
+			compatible = "google,cros-ec-pwm";
+			#pwm-cells = <1>;
+			google,max-pwms = <4>;
+		};
+	};
-- 
2.8.0.rc3.226.g39d4020