o Don't make the SER_INT_* defines visible to userland. They

are related to internals, not user-visible state.
o  Add a typedef for serdev_intr_t and protect it with !LOCORE.

sys/sys/serial.h

@@ -65,6 +65,7 @@
 
 #define	SER_MASK_DELTA	SER_DELTA(SER_MASK_STATE)
 
+#ifdef _KERNEL
 /*
  * Specification of interrupt sources typical for serial ports. These are
  * useful when some umbrella driver like scc(4) has enough knowledge of
@@ -82,4 +83,10 @@
 #define	SER_INT_MASK	0xff0000
 #define	SER_INT_SIGMASK	(SER_MASK_DELTA | SER_MASK_STATE)
 
+#ifndef LOCORE
+typedef int serdev_intr_t(void*);
+#endif
+
+#endif	/* _KERNEL */
+
 #endif /* !_SYS_SERIAL_H_ */