arm64: dts: rockchip: Add OneThing Edge Cube series

arm64: dts: rockchip: Add OneThing Edge Cube series

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.

Other than the difference in RAM capacity, the OEC and OEC-turbo are
identical in all other specifications.

  Specification:
    - Rockchip RK3566
    - LPDDR4X 2GB (OEC) / 4GB (OEC-turbo)
    - eMMC 8GB
    - Gigabit Ethernet port x 1
    - USB 3.0 port x 1
    - USB-C 2.0 port x 1
    - 12V DC Power supply
    - SATA 3.0 connector x 1

These devices do not have a PMIC, and their hardware circuit design
is highly similar to that of the rk3566-box-demo[1]. Hardware schematics
are not available at this time, with the vendor firmware dts available
for reference[2].

Ethernet, USB 3.0 and SATA 3.0 ports tested, all working well.

[1] https://elixir.bootlin.com/linux/v6.18.6/source/arch/arm64/boot/dts/rockchip/rk3566-box-demo.dts
[2] https://archive.org/download/wxy-oec-RK3566-4G-dump/wxy-oec-RK3566-4G-dump.dts

Signed-off-by: Jun Yan <jerrysteve1101@gmail.com>
Link: https://patch.msgid.link/20260214021719.620752-4-jerrysteve1101@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>