/usr/include/ is in libqt5serialport5-dev 5.2.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/qt5/
/usr/include/qt5/QtSerialPort/
/usr/include/qt5/QtSerialPort/qserialportinfo.h
/usr/include/qt5/QtSerialPort/QtSerialPortDepends
/usr/include/qt5/QtSerialPort/QSerialPort
/usr/include/qt5/QtSerialPort/qtserialportversion.h
/usr/include/qt5/QtSerialPort/QLockFile
/usr/include/qt5/QtSerialPort/QWinEventNotifier
/usr/include/qt5/QtSerialPort/QtSerialPortVersion
/usr/include/qt5/QtSerialPort/QtSerialPort
/usr/include/qt5/QtSerialPort/qwineventnotifier.h
/usr/include/qt5/QtSerialPort/qserialportglobal.h
/usr/include/qt5/QtSerialPort/QSerialPortInfo
/usr/include/qt5/QtSerialPort/qlockfile.h
/usr/include/qt5/QtSerialPort/qserialport.h