The code is there. It should work...

initramfs/init

@@ -84,18 +84,30 @@ fi
 info "checking for network configuration on kernel commandline"
 echo ""
 for var in $(cat /proc/cmdline); do
-    if [[ ${var/=*} = ipcmd ]]; then
+    case "${var/=*}" in
         # Split the "value" part of this parameter into parts, with "," as
-        # separators and then use them for constructing iproute2 commandline.
+        # separators and then use them for constructing iproute2 or brctl
+        # commandline.
         # Don't do any input validation; escape to the shell if things break.
         # Do it in a subshell to prevent IFS change leak.
-        (
-            IFS=","
-            set -- ${var/*=}
-            info "ip ${@}"
-            /busybox ip ${@}
-            isok $?
-        )
+        ipcmd) 
+            (
+                IFS=","
+                set -- ${var/*=}
+                info "ip ${@}"
+                /busybox ip ${@}
+                isok $?
+            )
+        ;;
+        brctl)
+            (
+                IFS=","
+                set -- ${var/*=}
+                info "brctl ${@}"
+                /busybox brctl ${@}
+                isok $?
+            )
+        ;;
     fi
 done