Added custom platform option

src/BuildOpt.h

@@ -14,6 +14,7 @@
  * RADIOLIB_PIN_TYPE - which type should be used for pin numbers in functions like digitalRead().
  * RADIOLIB_PIN_MODE - which type should be used for pin modes in functions like pinMode().
  * RADIOLIB_PIN_STATUS - which type should be used for pin values in functions like digitalWrite().
+ * RADIOLIB_DIGITAL_PIN_TO_INTERRUPT - function to be used to convert digital pin number to interrupt pin number.
  * RADIOLIB_INTERRUPT_STATUS - which type should be used for pin changes in functions like attachInterrupt().
  * RADIOLIB_NC - alias for unused pin, usually the largest possible value of RADIOLIB_PIN_TYPE.
  * RADIOLIB_SOFTWARE_SERIAL_UNSUPPORTED - defined if the specific platform does not support SoftwareSerial.
@@ -21,7 +22,11 @@
  * RADIOLIB_TONE_UNSUPPORTED - some platforms do not have tone()/noTone(), which is required for AFSK.
  *
  * In addition, some platforms may require RadioLib to disable specific drivers (such as ESP8266).
+ *
+ * Users may also specify their own configuration by defining all of the platform-specific parameters
+ * and macro RADIOLIB_CUSTOM_PLATFORM prior to including the main library file (RadioLib.h).
  */
+#if !defined(RADIOLIB_CUSTOM_PLATFORM)
   #if defined(__AVR__) && !(defined(ARDUINO_AVR_UNO_WIFI_REV2) || defined(ARDUINO_AVR_NANO_EVERY))
     // Arduino AVR boards (except for megaAVR) - Uno, Mega etc.
     #define RADIOLIB_PLATFORM                           "Arduino AVR"
@@ -178,6 +183,7 @@
     #define RADIOLIB_NC                                 (0xFF)
 
   #endif
+#endif
 
 /*
  * Uncomment to enable debug output.