of: Add descriptions of thermtrip properties to Tegra PMC bindings

Hardware-triggered thermal reset requires configuring the I2C
reset procedure. This configuration is read from the device tree,
so document the relevant properties in the binding documentation.
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-pmc.txt

@@ -47,6 +47,23 @@ Required properties when nvidia,suspend-mode=<0>:
   sleep mode, the warm boot code will restore some PLLs, clocks and then
   bring up CPU0 for resuming the system.
 
+Hardware-triggered thermal reset:
+On Tegra30, Tegra114 and Tegra124, if the 'i2c-thermtrip' subnode exists,
+hardware-triggered thermal reset will be enabled.
+
+Required properties for hardware-triggered thermal reset (inside 'i2c-thermtrip'):
+- nvidia,i2c-controller-id : ID of I2C controller to send poweroff command to. Valid values are
+                             described in section 9.2.148 "APBDEV_PMC_SCRATCH53_0" of the
+                             Tegra K1 Technical Reference Manual.
+- nvidia,bus-addr : Bus address of the PMU on the I2C bus
+- nvidia,reg-addr : I2C register address to write poweroff command to
+- nvidia,reg-data : Poweroff command to write to PMU
+
+Optional properties for hardware-triggered thermal reset (inside 'i2c-thermtrip'):
+- nvidia,pinmux-id : Pinmux used by the hardware when issuing poweroff command.
+                     Defaults to 0. Valid values are described in section 12.5.2
+                     "Pinmux Support" of the Tegra4 Technical Reference Manual.
+
 Example:
 
 / SoC dts including file
@@ -68,6 +85,15 @@ pmc@7000f400 {
 
 / Tegra board dts file
 {
+	...
+	pmc@7000f400 {
+		i2c-thermtrip {
+			nvidia,i2c-controller-id = <4>;
+			nvidia,bus-addr = <0x40>;
+			nvidia,reg-addr = <0x36>;
+			nvidia,reg-data = <0x2>;
+		};
+	};
 	...
 	clocks {
 		compatible = "simple-bus";