description:i found the MACRO :
#elif defined(NRF52) #if (UART_EASY_DMA_SUPPORT == 1)
question : is the dma is special with nrf52?
This is all in the nrf52 manual. nRF52 has EasyDMA on lots of peripherals and the nRF51 didn't have it, and some/most/all of the drivers now support it.
What is your actual question?