Drats! How I missed it! Indeed, it's between 6255 and CPU! Thank you alot Now it'll go much better!
Update: the TX and RX names must be the other way around (e.g. TX is CPU's RX and RX is CPU's TX); other than that, works fine!
It must be some Chinese tradition to exchange RX and TX markings; I've encountered it in other chinese boards as well...
After booting it drops directly into root shell on the serial console