dt-bindings: gpio: rockchip: Allow use of a power-domain

dt-bindings: gpio: rockchip: Allow use of a power-domain

The GPIO controllers in most Rockchip SoCs are part of power domains
that are always powered on, i.e. PD_BUS or PD_PMU. These always powered
on power domains have typically not been described in the device tree.

Because these power domains have been left out of the device tree there
has not been any real need to properly describe the GPIO controllers
power domain.

On RK3528 the GPIO controllers are spread out among the described
PD_RKVENC, PD_VO and PD_VPU power domains. However, one GPIO controller
belong to an undescribed always powered on power domain.

Add support to describe an optional power-domains for the GPIO
controllers in Rockchip SoCs.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250723085654.2273324-2-jonas@kwiboo.se
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>