rbus_new
rbus_tag_t rbus_new(rbus_tag_t, bus_addr_t, bus_size_t, bus_addr_t, int);
rct.iobustags[minbus]=rbus_new(caa->ca_rbus_iot,
rct.membustags[minbus]=rbus_new(caa->ca_rbus_memt,
rct.iobustags[busnum]=rbus_new(rct.iobustags[busparent],
rct.membustags[busnum]=rbus_new(rct.membustags[busparent],