Buy a million and sign some NDA's, but then you can't share the datasheet nor use it to make an open source driver..
Wait till someone reverse engineer it, or do it yourself..
And even if you had a datasheet, you dont have the code running in the SuperIO chip, so the datasheet is not all that usefull without the code, and the code is signed and encrypted so its also not easy to extract it from the BIOS binary/rom.