This question came up in SIG-Attestation discussion 2022/03/29, where it could be used for things like X.509 extensions.
https://pen.iana.org/pen/PenApplication.page is the application process (30 days, no cost), and there's lots of other Foundations and Consortiums on the list who have done it, at https://www.iana.org/assignments/enterprise-numbers/enterprise-numbers