Add new config option OPENTHREAD_CONFIG_DEFAULT_CHILD_TIMEOUT in header file (#1712)

src/core/openthread-core-default-config.h

@@ -179,6 +179,16 @@
 #define OPENTHREAD_CONFIG_MAX_CHILDREN                          10
 #endif  // OPENTHREAD_CONFIG_MAX_CHILDREN
 
+/**
+ * @def OPENTHREAD_CONFIG_DEFAULT_CHILD_TIMEOUT
+ *
+ * The default child timeout value (in seconds).
+ *
+ */
+#ifndef OPENTHREAD_CONFIG_DEFAULT_CHILD_TIMEOUT
+#define OPENTHREAD_CONFIG_DEFAULT_CHILD_TIMEOUT                 240
+#endif // OPENTHREAD_CONFIG_DEFAULT_CHILD_TIMEOUT
+
 /**
  * @def OPENTHREAD_CONFIG_IP_ADDRS_PER_CHILD
  *

src/core/thread/mle_constants.hpp

@@ -100,8 +100,8 @@ enum
     kMaxLeaderToRouterTimeout   = 90,               ///< INFINITE_COST_TIMEOUT (seconds)
     kReedAdvertiseInterval      = 570,              ///< REED_ADVERTISEMENT_INTERVAL (seconds)
     kReedAdvertiseJitter        = 60,               ///< REED_ADVERTISEMENT_JITTER (seconds)
-    kMleEndDeviceTimeout        = 240,              ///< MLE_END_DEVICE_TIMEOUT (seconds)
     kLeaderWeight               = 64,               ///< Default leader weight for the Thread Network Partition
+    kMleEndDeviceTimeout        = OPENTHREAD_CONFIG_DEFAULT_CHILD_TIMEOUT,  ///< MLE_END_DEVICE_TIMEOUT (seconds)
 };
 
 enum