SBI v0.2 is more scalable and extendable to handle future needs for RISC-V supervisor interfaces. For example, with SBI v0.2 HSM extension, only a single hart need to boot and enter operating system. The booting hart can bring up secondary harts one by one afterwards. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Atish Patra <atish.patra@wdc.com>