dt-bindings: HID: i2c-hid: elan: add 'no-reset-on-power-off' property

When the power supply is shared with other peripherals the reset line
can be wired in such a way that it can remain deasserted regardless of
whether the supply is on or not.

This is important as it can be used to avoid holding the controller in
reset for extended periods of time when it remains powered, something
which can lead to increased power consumption. Leaving reset deasserted
also avoids leaking current through the reset circuitry pull-up
resistors.

Add a new 'no-reset-on-power-off' devicetree property which can be used
by the OS to determine when reset needs to be asserted on power down.

Note that this property can also be used when the supply cannot be
turned off by the OS at all.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240507144821.12275-4-johan+linaro@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

Author: jhovold

Documentation/devicetree/bindings/input/elan,ekth6915.yaml

@@ -36,6 +36,12 @@ properties:
   reset-gpios:
     description: Reset GPIO; not all touchscreens using eKTH6915 hook this up.
 
+  no-reset-on-power-off:
+    type: boolean
+    description:
+      Reset line is wired so that it can (and should) be left deasserted when
+      the power supply is off.
+
   vcc33-supply:
     description: The 3.3V supply to the touchscreen.