Beaglebone Black eMMC pin Muxing in u-boot

Hello 

          I'm using Beaglebone black I've basic doubt on eMMC pin muxing in u-boot. 

In schematic eMMC connecting as MMC1_DAT[7..0], which means data0 to data8. But in u-boot source code mux.c defined as 

static struct module_pin_mux mmc1_pin_mux[] = {
{OFFSET(gpmc_ad3), (MODE(1) | RXACTIVE | PULLUP_EN)}, /* MMC1_DAT3 */
{OFFSET(gpmc_ad2), (MODE(1) | RXACTIVE | PULLUP_EN)}, /* MMC1_DAT2 */
{OFFSET(gpmc_ad1), (MODE(1) | RXACTIVE | PULLUP_EN)}, /* MMC1_DAT1 */
{OFFSET(gpmc_ad0), (MODE(1) | RXACTIVE | PULLUP_EN)}, /* MMC1_DAT0 */
{OFFSET(gpmc_csn1), (MODE(2) | RXACTIVE | PULLUP_EN)}, /* MMC1_CLK */
{OFFSET(gpmc_csn2), (MODE(2) | RXACTIVE | PULLUP_EN)}, /* MMC1_CMD */
{OFFSET(gpmc_csn0), (MODE(7) | RXACTIVE | PULLUP_EN)}, /* MMC1_WP */
{OFFSET(gpmc_advn_ale), (MODE(7) | RXACTIVE | PULLUP_EN)}, /* MMC1_CD */
{-1},
};

How its possible and also its working fine. u-boot consider as normal mmc or any technical details behind this?

Thanks

Kumar