Tegra External Temperature Sensor driver
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This file documents the DT bindings of the NCT1008 external temperature sensor
driver. NCT1008 belongs to a class of sensors that reports two temperatures,
one local and one external. On Tegra systems the local sensor measures the
board temperature and the external sensor measures the junction temperature on
the die. The sensor is connected as an I2C slave and can be communicated with
using the SMBus protocol. The Tegra NCT1008 driver supports TMP451 and MAX6649
in addition to the NCT1008 sensor.

NCT1008 driver is an I2C client that registers itself as two sensors to
the thermal framework and supports programmable temperature alerts and
overtemperature shutdown limits. The sensor ids are defined in
<dt-bindings/misc/nvidia,nct1008.h>.

Required properties :
- compatible : The compatibility string must match the sensor that is
  being used and should be one of the following:
  - onsemi,nct72
  - ti,tmp451
  - maxim,max6649
- reg : An I2C client property which specifies the slave address of the sensor
  on the I2C bus.
- #thermal-sensor-cells : Should be 1. See ./thermal.txt for a description of
  this property.
- conv-rate : Specifies the value to be programmed into the conversion rate
  register of the sensor. Valid range is 0 - 9. See the sensor datasheet for the
  exact conversion rates.

Optional properties :
- interrupts : An I2C client property which specifies the interrupt used by the
  sensor for temperature alerts.
- temp-alert-gpio : This property specifies the gpio used by the sensor to
  trigger the temperature alert.
- loc-shutdown-limit : When present, this property specifies the temperature at
  which the local sensor will assert the thermal trigger signal to the
  Power Management IC. which can be configured to reset or shutdown the device.
  In the absence of this property the over temperature shutdown from local
  sensor will be disabled. Can take any value in the valid temperature range of
  the sensor.
- ext-shutdown-limit : Similar to the loc-shutdown-limit. Used to specify the
  over temperature shutdown limit for the external sensor.
- extended-range : This property is used to control the range of temperature
  measurement in the sensor. Allowed values are 0,1. A value of 1 enables
  extended temperature monitoring range and a missing property disables it.
- offset : Specifies the offset to be programmed to the offset register. The
  property is in units of 0.25C and has a valid range of -128C to 127C.
- offset-hi-res : Similar to the offset property but allows offset to be
  programmed in units of 0.0625C.
- support-fuse-offset : When present the driver reads the fuse registers which
  has the measured offset at a known temperature. After performing linear
  correction on the true physical temperature (which is offset + known
  temperature) a value for offset and nfactor are calculated. These values are
  then used to program the corresponding registers in the sensor hardware. The
  property takes no value.
- alpha : Specifies the slope of the linear correction that is performed when
  support-fuse-offset is specified.
- beta : Specifies the intercept of the linear correction that is performed when
  support-fuse-offset is specified.

Note:
The external temperature reported by the sensor can often be inaccurate which
can be corrected by progamming the offset register. The NCT1008 driver allows
offset to be specified in couple of ways as using the various offset properties
described above. The support-fuse-offset property takes effect only if both
offset and offset-hi-res are absent. The offset-hi-res property takes effect
only if offset property is absent.