dt-bindings: clock: mediatek: Describe MT8196 clock controllers

dt-bindings: clock: mediatek: Describe MT8196 clock controllers

Introduce binding documentation for system clocks, functional clocks,
and PEXTP0/1 and UFS reset controllers on MediaTek MT8196.

This binding also includes a handle to the hardware voter, a
fixed-function MCU designed to aggregate votes from the application
processor and other remote processors to manage clocks and power
domains.

The HWV on MT8196/MT6991 is incomplete and requires software to manually
enable power supplies, parent clocks, and FENC, as well as write to both
the HWV MMIO and the controller registers.
Because of these constraints, the HWV cannot be modeled using generic
clock, power domain, or interconnect APIs. Instead, a custom phandle is
exceptionally used to provide direct, syscon-like register access to
drivers.

Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Co-developed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Laura Nao <laura.nao@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>