Memory Technology Devices are flash, RAM and similar chips, often
used for solid state file systems on embedded devices. This option
will provide the generic support for MTD drivers to register
themselves with the kernel and for potential users of MTD devices
to enumerate the devices which are present and obtain a handle on
them. It will also allow you to select individual drivers for
particular hardware and users of MTD devices. If unsure, say N.

source code:

/arch/mips/cavium-octeon/flash_setup.c