Hi, I would like to add a new brand and a new device. CAN Star Treasure Box comes with OpenWrt installed. Here's info from the datasheet:
Wireless B/G/N/AC speed up to 1200Mbps Support AP,WISP wireless mode WAN port support PoE Out, PoE voltage 12v=2.0a Support PoE Pass-through 2x2 MIMO Technology Passive PoE supports up to 100 meter 512MB SDRAM 128MB Flash,770Mhz CPU IPQ 4109 OPENWRT and DDWRT Firmware
https://www.mobipromo.io/pages/product.html
Looks like it's IPQ4019. So you can probably use an existing IPQ4019 device as a start. At least it isn't Broadcom-based...
Since it appears to be only marketed in mainland China, there is unfortunately a high chance that the OEM is violating the GPL and not providing kernel source. Otherwise, you'd probably be able to find a lot of the "important" parameters such as flash memory layout in the kernel sources...
They claim OpenWRT - so ideally if they're marketing it, they've already provided their changes somewhere that could potentially be integrated into master.
(Sometimes this is easier said than done - see GL.iNet NAND support as an example, as many of GL.iNet's modifications were considered not acceptable upstream as-is.)