Turns out it's done by a lot of hard work rather than passively collecting rent: "Partnerships with large OEMs operate as signals that also generate barriers t

Turns out it's done by a lot of hard work rather than passively collecting rent: "Partnerships with large OEMs operate as signals that also generate barriers to imitation. As pointed out by one of our informants: “If a company like Samsung or TI is licensing from us, this means it may be difficult to develop our technology.” Multiple licenses create a psychological barrier to entry. In addition, the IP that is licensed needs to be complemented by ARM’s customer services and considerable expertise" from p22 of here https://www.ifm.eng.cam.ac.uk/uploads/Research/CTM/working_paper/2015-02-Ferriani-Garnsey-Lorenzoni-Massa.pdf https://www.ifm.eng.cam.ac.uk/uploads/Research/CTM/working_p... So I suppose somebody could make an ARM clone but they'd have to actually do it. An actual licensee would surely be prohibited by the license though.