dt-bindings: i2c: i2c-rk3x: Allow use of a power-domain

dt-bindings: i2c: i2c-rk3x: Allow use of a power-domain

The I2C 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 I2C controllers
power domain.

On RK3528 the I2C controllers are spread out among the described
PD_RKVENC, PD_VO and PD_VPU power domains. However, one I2C controller
belong to an undescribed always powered on power domain.

Add support to describe an optional power-domains for the I2C
controllers in Rockchip SoCs.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20250723085654.2273324-3-jonas@kwiboo.se