This isn't an exhaustive list, but you should add new prefixes to it before
using them to avoid name-space collisions.
-abcn Abracon Corporation
abilis Abilis Systems
+abracon Abracon Corporation
actions Actions Semiconductor Co., Ltd.
active-semi Active-Semi International Inc
ad Avionic Design GmbH
via VIA Technologies, Inc.
virtio Virtual I/O Device Specification, developed by the OASIS consortium
vivante Vivante Corporation
+vocore VoCore Studio
voipac Voipac Technologies s.r.o.
wd Western Digital Corp.
wetek WeTek Electronics, limited.