Function esp_eth_get_mac_instance 

pub unsafe extern "C" fn esp_eth_get_mac_instance(
    hdl: *mut c_void,
    mac: *mut *mut esp_eth_mac_s,
) -> i32

@brief Get MAC instance memory address

@param[in] hdl handle of Ethernet driver @param[out] mac pointer to memory to store the instance @return esp_err_t - ESP_OK: success - ESP_ERR_INVALID_ARG: failed because of some invalid argument