Is it possible to use MDK-pro IP networking SLIP with SPI physical interface, which can run faster than UART?
Can it?
Check the datasheet: Most UARTs can go at mega bit/s rates - it's usually just the RS232 transceiver that limits the speed...
(or the desire/need to stick to "standard" baud rates)
UART is limited to 3.7Mbps (with 59MHz clock) or 5.5Mbps at overclocked 88MHz.
Most SPI can go at higher baudrates than corresponding UARTs for the reason that a UART normally sample the input at 8 or 16 times the baudrate - this to synchronize well with the start bit and still support baudrate errors without failing near the stop bit(s).
The SPI doesn't need that, since there is a dedicated clock signal that informs when it's time to sample the input. So while some UART can do Mbit/s, we instead have some SPI that can do 50Mbit/s or more.