After upgrading an iPhone and iPad to IOS 8, the iPad may “ring” every time a phone call is received on the iPhone for same id user account that is used on the iPad.  There is a setting in the FaceTime app that can be used to enable or disable this feature.  Go to Settings, FaceTime and turn on or off the “iPhone Cellular Calls”.  The description of feature “iPhone Cellular Calls” is “Use you iPhone cellular connection to make and receive calls when your iPhone is nearby and on Wi-Fi.”