Why does building digi RealPort (dgrp) 40002086_X6P.src.rpm fail with kernel-3.10.0-514.el7.x86_64 ?

Issue

• Building digi RealPort with kernel-3.10.0-514.el7.x86_64 with the errors as follows.

/root/rpmbuild/BUILD/dgrp-1.9/driver/build/dgrp_net_ops.c: In function 'dgrp_input':
/root/rpmbuild/BUILD/dgrp-1.9/driver/build/dgrp_net_ops.c:535:31: error: 'TTY_CLOSING' undeclared (first use in this function)
  if (tty->closing || test_bit(TTY_CLOSING, &tty->flags))
                               ^
./arch/x86/include/asm/bitops.h:344:25: note: in definition of macro 'test_bit'
  (__builtin_constant_p((nr))  \
                         ^
/root/rpmbuild/BUILD/dgrp-1.9/driver/build/dgrp_net_ops.c:535:31: note: each und
eclared identifier is reported only once for each function it appears in
  if (tty->closing || test_bit(TTY_CLOSING, &tty->flags))
                               ^
./arch/x86/include/asm/bitops.h:344:25: note: in definition of macro 'test_bit'
  (__builtin_constant_p((nr))  \
                         ^
make[3]: *** [/root/rpmbuild/BUILD/dgrp-1.9/driver/build/dgrp_net_ops.o] Error 1
make[2]: *** [_module_/root/rpmbuild/BUILD/dgrp-1.9/driver/build] Error 2
make[2]: Leaving directory `/usr/src/kernels/3.10.0-514.el7.x86_64'
make[1]: *** [build] Error 2
make[1]: Leaving directory `/root/rpmbuild/BUILD/dgrp-1.9/driver/2.6.27'
make: *** [build] Error 2
error: Bad exit status from /var/tmp/rpm-tmp.q6vgWk (%build)