Not really severely. It has a few questionable tweaks here and there.
The questionable part is CPU companies not pushing for upstream integration, so you get e.g. Qualcomm Linux. In fact, the process is not pushing, it is pulling. (some people have started working on it, still long way off)
It can be done, as shown by efforts by TI, ARM and many more...
Hell, even Rockchip, Allwinner and Sony can do it, Qualcomm, Mediatek, Google and Samsung are just not doing it because they are able to skate by without doing it.
The funny part is on Windows Phone, Microsoft learned from the kernel development process and made Samsung, LG, HTC, et all upstream their drivers, whereas Google in the same position with the same vendors has not done this and thus Sony is the only OEM pushing drivers upstream.
Upstream Allwinner support is a community effort, and it takes so long to convince the kernel developers to merge code that parts are generally years obsolete by the time they're fully supported. I think the upstream support may almost be at the point that C.H.I.P could use it - but they're using a single-core SoC from early 2012. I've seen patches for basic functionality like clock controllers (without which nothing works) get stuck in endless mailing list arguments about the most elegant approach, contradictory requirements from different maintainers, all sorts. It's not working.
The kernels used by actual Allwinner-based Android devices have almost nothing in common with the upstream support. They use a completely different mechanism for describing the hardware configuration, a completely different set of drivers, and are based on a kernel that predates upstream support.
True, but what has been accomplished with the Linux Sunxi community is a shortening of that loop to bring up new boards with modern kernels, the Pine A64 for example took only a year to gain support[1], and that was around the time they actually started shipping in quantity. Additionally, many of the ethernet drivers, HDMI PHY drivers, Cedrus (provides H.264 & H.265 decoding @ 10bit) are reusable on new chips like the H5[2].
I would not expect much from Allwinner directly, but at this point there is a sizable ecosystem and mainline support for most of their chips, which can't be said for most other ARM vendors. Another aspect of this is Allwinner sells most of their chips thru multiple business units, with the silicon being exactly the same, just what is silkscreened on the top of the package being different[3].
The A64 was one of the chips whose clock controller support got stuck in mailing list hell for over a year. Currently that's planned for 4.10, basic stuff like Ethernet, USB and SD card support is still pending though: http://linux-sunxi.org/Linux_mainlining_effort I imagine they must be using a ton of patches on top of mainline to make that work.
