In oMigen we had four kinds of things that in nMigen go to extras:

• Drive(x)
• IOStandard(x)
• Misc("K=V")
• Misc("K")

All of these with the exception of the last are essentially key-value pairs. The last one appears to be almost exclusively used as Misc("PULLUP") on Xilinx platforms, and it could as well be replaced with PULLUP=TRUE (this is done for Sayma).

To reduce the amount of ad-hoc mini-languages, let's just use a dict instead.