nvram_read_macaddr
nvram_read_macaddr(prefix, "et0macaddr", sprom->et0mac, fallback);
nvram_read_macaddr(prefix, "et1macaddr", sprom->et1mac, fallback);
nvram_read_macaddr(prefix, "et2macaddr", sprom->et2mac, fb);
nvram_read_macaddr(prefix, "macaddr", sprom->il0mac, fallback);
nvram_read_macaddr(prefix, "il0macaddr", sprom->il0mac, fallback);
nvram_read_macaddr(NULL, "et0macaddr", mac, false);