UEFI’s Tianocore implementation has built-in support for Intel/AMD and ARM. The RISCV-V port has been in a branch. Now it appears RISC-V is about to become part of the main branch, with 2 new packages, RiscVPkg and RiscVVirtPkg:
RISC-V is a new ISA which was designed to support computer architecture research and education. But now it becomes a standard open architecture for industry implementations. RISC-V edk2 project is to create a new processor binding in UEFI spec and to have RISC-V edk2 implementation. The goal is to have RISC-V edk2 port as the firmware reference for RISC-V platforms. Also, this proves the UEFI spec and edk2 implementation are flexible and well deisgned for adopting any processor architecture. The following modules are related to edk2 RISC-V port:
RiscVPkg – RISC-V processor package. This package provides RISC-V processor related protocols/libraries accroding to UEFI specification and edk2 implementations.
RiscVVirtPkg – RISC-V QEMU port. This is the RISC-V platform which is based on QEMU implementation. We use PC/At bus architecture as RISC-V platform bus spec. The image built from this package can be launched by QEMU RISC-V port.
https://bugzilla.tianocore.org/show_bug.cgi?id=2532
https://bugzilla.tianocore.org/show_bug.cgi?id=2533
Firmware Security 
The latest branch we’re developing on is not RISC-V but https://github.com/tianocore/edk2-staging/tree/RISC-V-V2.
Also RiscVVirtPkg with the PC/AT architecture is likely not getting integrated – the patches for QEMU are no longer developed.
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Our status is tracked here: https://github.com/riscv/riscv-uefi-edk2-docs
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