CONFIG_MMC_SDHCI_EXTERNAL_DMA (not configurable)

configname: CONFIG_MMC_SDHCI_EXTERNAL_DMA

Linux Kernel Configuration
└─>Device Drivers
└─>MMC/SD/SDIO card support
└─>MMC_SDHCI_EXTERNAL_DMA
In linux kernel since version 5.1 (release Date: 2019-05-05)  
depends
CONFIG_MMC