Debugging instructions (system mostly)

README.md

@@ -6,5 +6,8 @@ Juraj's Blog, mostly:
 - https://jborza.com/post/2021-04-04-riscv-supervisor-mode/
 - https://jborza.com/emulation/2021/04/22/ecalls-and-syscalls.html
 
+RISC-V SBI Specifications:
+- https://github.com/riscv-non-isa/riscv-sbi-doc/releases
+
 Buildroot fork for nommu linux:
 - https://github.com/regymm/buildroot