Companies like Freescale and Texas Instruments provide good software support, and documentation, which is why they can be found in many embedded devices, because without documentation or source code low-level customization is nearly impossible or extremely time consuming. They also usually open most of the documentation and code, because they understand this can foster the use of their chips. On the other hand, Chinese-based SoC manufacturers focus on high-volume platforms such as tablets and smartphones, and usually management don’t understand the advantage to make documentation and GPL source code available, or even may consider it bad for business.
Some individuals and small companies do not see it that way however, and they either want to access to the source code to improve existing mobiles devices, or use low cost Chinese SoCs to provide highly customizable hardware and software solutions. So source code and documentation have started to leak, and tools (reverse-engineered or leaked) are also available. The most active community is linux-sunxi with members working on AllWinner SoCs. They have a wiki, a source code repo, and IRC channel and mailing list for communications. Their work helped the proliferation of AllWinner based development boards (Cubieboard, A13-Olinuxino, pcDuino…) that people now use for all sorts of things. It’s not exactly perfect, especially when it comes to documentation, but it’s a massive progress compared to just one or two years ago, and AllWinner now even post source code release news on their own website.
Following the GPL source code releases, there has been several individuals working on Linux support for Rockchip RK3066 and RK3188 SoC, which saw the release of PicUntu, initial Linux support on RK3188, and even basic mainline support. I’ve also found out that the full RK3066 Technical Reference Manual (1142 pages) has been leaked recently. With Rockchip SoCs becoming popular again, and since source code, and some documentation are now freely available, linux-rockchip community has recently been put together. They have a wiki, and communicate via #linux-rockchip IRC channel on Freenode. They are not quite as organized as linux-sunxi community yet, with no specific community repo or mailing list, but hey, you have to start somewhere, and if you want to get involved join them on IRC.
Beside individuals working on the software, I’ve seen people behind the Cubieboard (Tom Cubie), and Olimex (Tsvetan Usunov) openly interested in Rockchip RK3066, RK3168, or RK3188 SoC, so it’s very possible CubieRock or/and RK3188-OlinuXino boards (I made those names up) could become available in the next few months, provided there’s no road block.