It's usually preferred that the mainline kernel be used.
For this case, maybe if you strip out the patches [specifically for the Rockchip] from that repo, create a new target, and put them there, it should be fine I guess.
I guess there's also the work of convincing people that you will maintain the architecture.
But, there is no clear-cut yes/no answer to your question.
Try to do it, show it to the community, and let's see.
The only recommendation [I personally have] is to have fun while doing it [ even if the target does not reach the mainline LEDE tree ].
I could add, that the LEDE/OpenWrt project does not (yet) have a way for having out-of-tree targets.
Unless I am mistaking.
If I am not mistaking, it would be interesting to have [as a general thought]
Not sure.
There might be some docs on the OpenWrt wiki.
I'm onmy phone right now, and can't look.
I'd just take a look at the target/linux folder and use one folder as base.
The targets are organized by chip/soc family.
And there are alsi subtargets, which can be specific boards.
