RISC-V：读作risk-five，是一个开源的CPU指令集架构
zephyr：开源操作系统
linux：没什么好说的。
risc-pk：The RISC-V Proxy Kernel。解释如下：is a lightweight application execution environment that can host statically-linked RISC-V ELF binaries. It is designed to support tethered RISC-V implementations with limited I/O capability and and thus handles I/O-related system calls by proxying them to a host computer.
BBL ：the Berkeley Boot Loader。
linux相关开源基础库对RISC-V的支持
binutils: upstreamed (2.28 is the first release with RISC-V support)
gcc: upstreamed (7.1 is the first release with RISC-V support)
glibc: upstreamed (2.27 is the first release with RISC-V support)
linux kernel: upstreamed (the architecture core code went into
kernel 4.15; kernel 4.19 contains all drivers necessary for booting a
simulated system to userland)
gdb: upstreamed in master (in the release process)
qemu: upstreamed (2.12 is the first release with RISC-V support)
