@Prodatron, drivers for the SD-Mapper v1 and v2 would also be very welcome. 
PS: v1 and v2 have different register sets.
Are these new hardware?
Being "new" is relative in this case. But you can say that they're somewhat new. 😅 The v1 is from ~9 years ago, and the v2 is from ~3 years ago.
Mega SD etc is something different? I should have a look at this. Maybe you have a link?
Yes, they're different from the MegaSD. Both are Open Hardware licensed under the CERN OHL. Many different makers, from different countries, are making interfaces based on these designs. It's intended to be libre and have an affordable price.
The older SD-Mapper v1 documentation and Nextor driver sources can be found here.
The SD-Mapper v2 is a complete overhaul of the design, with many improvements to make it more efficient and allow for higher speed. It also supports card hot swap. Its documentation and Nextor driver sources can be found here.
Their Nextor drivers have the documentation about the register set of the respective interface at the very beginning of the file.
The v2 uses an ASCII16 ROM mapper and the SDcard interface register set is only shown at page-7.
