This option is used to indicate that the system-on-a-chip (SOC)
supports Multiprocessing. Multiprocessor support implemented above
the CPU core definition and currently needs to be selected manually.

Multiprocessor support is implemented with external cache and
interrupt controllers.

The MX interrupt distributer adds Interprocessor Interrupts
and causes the IRQ numbers to be increased by 4 for devices
like the open cores ethernet driver and the serial interface.

You still have to select "Enable SMP" to enable SMP on this SOC.