Here is what I have found as raw material:
http://projects.goldelico.com/p/gta04-kernel/issues/698/ http://comments.gmane.org/gmane.linux.kernel.mmc/5498 http://elinux.org/BeagleBoardPinMux#MMC2_via_TXS0206_or_TXS02612 http://gumstix.8.x6.nabble.com/OMAP3xxx-hsmmc-MMC3-doesn-t-work-always-times...
So it looks as if others did have similar plans - but no solution.
Basically we should design a DT node like
/ { mmc-expander { compatible = “ti,txs02612”; mmc = <&mmc1>; select-gpio = <&gpio3 18 0>; /* GPIO3_82 */ ports { eMMC: port@0 { reg = <0>; bus-width: 8; }; usd: port@1 { bus-width: 4; reg = <1>; }; }; };
The driver should register itself as a client (like a wifi driver) with mmc1 and register two new mmc interfaces.
But as discussed, this is not highest priority.
BR, Nikolaus