dt-bindings: arm: rockchip: Add OneThing Edge Cube series

dt-bindings: arm: rockchip: Add OneThing Edge Cube series

Add devicetree binding for the OneThing OEC and OEC-turbo

The OneThing Edge Cube (OEC) series features the RK3566 SoC, 8GB
eMMC storage, and supports one SATA interface, one Gigabit Ethernet
port, and one USB 3.0 port.
Among the lineup, the standard OEC model comes with 2GB of RAM, while
the OEC-turbo features 4GB of RAM; The rest of the specifications are
identical.

The OneThing Edge Cube series (shipping with the vendor firmware) is
originally designed as a PCDN (P2P Content Delivery Network) device.

Signed-off-by: Jun Yan <jerrysteve1101@gmail.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20260214021719.620752-3-jerrysteve1101@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>