dts: bindings: vendor-prefixes: add openisa

OpenISA is used as vendor for drivers for the rv32m1 cores.

Signed-off-by: Karsten Koenig <karsten.koenig.030@gmail.com>
diff --git a/dts/bindings/vendor-prefixes.txt b/dts/bindings/vendor-prefixes.txt
index 566be5a..75a202e 100644
--- a/dts/bindings/vendor-prefixes.txt
+++ b/dts/bindings/vendor-prefixes.txt
@@ -299,6 +299,7 @@
 ontat	On Tat Industrial Company
 opalkelly	Opal Kelly Incorporated
 opencores	OpenCores.org
+openisa	open-isa.org
 openrisc	OpenRISC.io
 option	Option NV
 oranth	Shenzhen Oranth Technology Co., Ltd.