You can find the complete source to the MTD driver library under bsp_root/libs/src/hardware/flash/mtd-flash.
The callouts are grouped by manufacturer (e.g. intel/iCFI_write.c). Each of these files contains enough comments to detail the type of flash they work with. These comment-blocks provide the most up-to-date information on selecting the right MTD callout. Don't be afraid to look at these files.