Earlier in 2011, MediaTek merged with Ralink Technology Corporation. See their products here: http://www.mediatek.com/_en/01_products/04_pro.php?sn=1057 A quite good source for product briefs on MediaTek/Ralink SoCs in pdf-form seems to be here: http://wikidevi.com/files/Ralink/.
In OpenWrt all MediaTek/Ralink SoCs are merge under the target
ramips. Available subtargets are:
Note that in OpenWrt builds the targets require target-specific firmware (that is, most devices need customised firmware). The kernel is patched with the command line that has the board name in it. This is like ar71xx boards, which are board-specific too.
See notes in OpenWrt dev wiki: https://dev.openwrt.org/wiki/ramips