dt-bindings: dpll: Add DPLL device and pin

Add a common DT schema for DPLL device and its associated pins.
The DPLL (device phase-locked loop) is a device used for precise clock
synchronization in networking and telecom hardware.

The device includes one or more DPLLs (channels) and one or more
physical input/output pins.

Each DPLL channel is used either to provide a pulse-per-clock signal or
to drive an Ethernet equipment clock.

The input and output pins have the following properties:
* label: specifies board label
* connection type: specifies its usage depending on wiring
* list of supported or allowed frequencies: depending on how the pin
  is connected and where)
* embedded sync capability: indicates whether the pin supports this

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20250704182202.1641943-2-ivecera@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>