Flash OTP regions can already be read via user space. Some boards have their serial number or MAC addresses stored in the OTP regions. Add support for them being a (read-only) nvmem provider. The API to read the OTP data is already in place. It distinguishes between factory and user OTP, thus there are up to two different providers. Signed-off-by: Michael Walle <michael@walle.cc> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20210424110608.15748-6-michael@walle.cc