main: restore support for flashing Espressif chips

This reverts commit 303410d3fc and also
removes the unnecessary fallback.

main.go

@@ -998,7 +998,8 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 			preferredPortIDs = append(preferredPortIDs, [2]uint16{uint16(vid), uint16(pid)})
 		}
 
-		var primaryPorts []string // ports picked from preferred USB VID/PID
+		var primaryPorts []string   // ports picked from preferred USB VID/PID
+		var secondaryPorts []string // other ports (as a fallback)
 		for _, p := range portsList {
 			if !p.IsUSB {
 				continue
@@ -1020,6 +1021,8 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 					continue
 				}
 			}
+
+			secondaryPorts = append(secondaryPorts, p.Name)
 		}
 		if len(primaryPorts) == 1 {
 			// There is exactly one match in the set of preferred ports. Use
@@ -1031,18 +1034,10 @@ func getDefaultPort(portFlag string, usbInterfaces []string) (port string, err e
 			// one device of the same type are connected (e.g. two Arduino
 			// Unos).
 			ports = primaryPorts
-		}
-
-		if len(ports) == 0 {
-			// fallback
-			switch runtime.GOOS {
-			case "darwin":
-				ports, err = filepath.Glob("/dev/cu.usb*")
-			case "linux":
-				ports, err = filepath.Glob("/dev/ttyACM*")
-			case "windows":
-				ports, err = serial.GetPortsList()
-			}
+		} else {
+			// No preferred ports found. Fall back to other serial ports
+			// available in the system.
+			ports = secondaryPorts
 		}
 	default:
 		return "", errors.New("unable to search for a default USB device to be flashed on this OS")