The physical layer for eMMC is SDIO- the same is used for SD cards, at least if you want more than ~ a megabyte/s of interface bandwidth. IIRC the layers above

The physical layer for eMMC is SDIO- the same is used for SD cards, at least if you want more than ~ a megabyte/s of interface bandwidth. IIRC the layers above SDIO are slightly different for eMMC and SD(HC), but generally SoCs that have SDIO interface support both types of memory.