The datasheet is a copyrighted document received under NDA. They literally can't.

And again, a datasheet from Allwinner is going to just tell you what the instantiation parameters for all the various IPs are. To write a driver for, I dunno, the I2C controller (or whatever, I know nothing about this SoC in particular) you're going to need a Synopsys databook or something.

There's a framework in place for distributing all that stuff between OEMs and first-tier customers. But with the exception of a handful of hardware vendors, no one's ever cared about getting it out to the public.

The datasheets are released and you can freely download them. For the Allwinner A64 documentation (another 64-bit SoC, which is very similar to H5) you can check https://linux-sunxi.org/A64#Documentation

And no, it is not a "stolen" or "leaked" documentation (I have actually seen such ridiculous claims in the phoronix forum). It is hosted on the Pine64 website with the permission from Allwinner. And the Pine64 people specifically asked Allwinner to remove the misleading "confidential" watermarks from the PDF files.

Allwinner H5 is very new and this Orange Pi PC 2 board is probably the very first piece of hardware using it. But I expect that the H5 documentation will become available in public access shortly. Just like the documentation for the older Allwinner chips. Maybe initially with the "confidential" watermark again, because the Allwinner people are a little bit lazy and don't seem to understand why the open source people are making so much fuss about this.