Start implement router

serial_link/protocol/frame_router.h

@@ -22,4 +22,8 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */
 
+#define UP_LINK 0
+#define DOWN_LINK 1
+
 void route_incoming_frame(uint8_t link, uint8_t* data, uint16_t size);
+void router_send_frame(uint8_t destination, uint8_t* data, uint16_t size);