1. optee_smccc_hvc() and optee_smccc_smc()
During optee_probe(), get_invoke_func() will return one of these two functions based on device tree configure.
And this returned invoke_fn will register to optee->invoke_fn for other functions to use.
And from the name, we can know optee_smccc_hvc() will trap to hypervisor(EL2), and optee_smccc_smc() will trap to monitor(EL3).
So when other functions,such as optee_do_call_with_arg(), call this optee->invoke_fn(), it could enter hypervisor(EL2) or monitor(EL3). It depends on device tree configuration?