target/riscv: explain why `arm` commands are used

src/target/riscv/riscv.c

@@ -1529,6 +1529,19 @@ extern __COMMAND_HANDLER(handle_common_semihosting_fileio_command);
 extern __COMMAND_HANDLER(handle_common_semihosting_resumable_exit_command);
 extern __COMMAND_HANDLER(handle_common_semihosting_cmdline);
 
+/*
+ * To be noted that RISC-V targets use the same semihosting commands as 
+ * ARM targets.
+ * 
+ * The main reason is compatibility with existing tools. For example the  
+ * Eclipse OpenOCD/SEGGER J-Link/QEMU plug-ins have several widgets to  
+ * configure semihosting, which generate commands like `arm semihosting 
+ * enable`. 
+ * A secondary reason is the fact that the protocol used is exactly the 
+ * one specified by ARM. If RISC-V will ever define its own semihosting 
+ * protocol, then a command like `riscv semihosting enable` will make 
+ * sense, but for now all semihosting commands are prefixed with `arm`. 
+ */
 static const struct command_registration arm_exec_command_handlers[] = {
 	{
 		"semihosting",