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
hannstar HannStar Display Corporation
haoyu Haoyu Microelectronic Co. Ltd.
hardkernel Hardkernel Co., Ltd
+hideep HiDeep Inc.
himax Himax Technologies, Inc.
hisilicon Hisilicon Limited.
hit Hitachi Ltd.
ontat On Tat Industrial Company
opalkelly Opal Kelly Incorporated
opencores OpenCores.org
+openrisc OpenRISC.io
option Option NV
ORCL Oracle Corporation
ortustech Ortus Technology Co., Ltd.