Firmware tpm
Intel and AMD each offers a tpm integrated into some of their CPUs, called "firmware TPM" or "fTPM". Rather than a separate tpm device, which requires installation on the board and may be expensive, fTPM is implemented directly in the CPU and is exposed via the firmware.
Intel offers the fTPM as Platform Trust Technology (PTT), generally available on 8th-generation or newer Core CPUs. It is compliant with TPM 2.0 specifications.
AMD offers fTPM on most of the Ryzen, Athlon and EPYC CPUs
From the user's perspective, an fTPM, once enabled in BIOS, looks exactly like a tpm 2.0, presenting the usual devices of /dev/tpmrm0
and /dev/tpm0.