NVIDIA Tegra124 and later SoCs support the multi-voltage level and
low power state of some of its IO pads. The IO pads can work in
the voltage of the 1.8V and 3.3V of IO voltage from IO power rail
sources. When IO interfaces are not used then IO pads can be
configure in low power state to reduce the power consumption from
that IO pads.

On Tegra124, the voltage level of IO power rail source is auto
detected by hardware(SoC) and hence it is only require to configure
in low power mode if IO pads are not used.

On T210 onwards, the auto-detection of voltage level from IO power
rail is removed from SoC and hence SW need to configure the PMC
register explicitly to set proper voltage in IO pads based on
IO rail power source voltage.

Add DT binding document for detailing the DT properties for
configuring IO pads voltage levels and its power state.

Signed-off-by: Laxman Dewangan <redacted>

---
Changes from V1:
 The DT binding document is modified to explain the regulator handle
 for different IOs and how can it be passed from the DT.
---
 .../bindings/pinctrl/nvidia,tegra-io-pad.txt       | 126 +++++++++++++++++++++
 1 file changed, 126 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt

diff --git a/Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt b/Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt
new file mode 100644
index 0000000..6ca961f
--- /dev/null
+++ b/Documentation/devicetree/bindings/pinctrl/nvidia,tegra-io-pad.txt

@@ -0,0 +1,126 @@
+NVIDIA Tegra PMC IO pad controller
+
+NVIDIA Tegra124 and later SoCs support the multi-voltage level and
+low power state of some of its IO pads. When IO interface are not
+used then IO pads can be configure in low power state to reduce
+the power from that IO pads. The IO pads can work in the voltage
+of the 1.8V and 3.3V of IO voltage from power rail sources.