+#define LEVT_EOL (1)
+#define LEVT_EOF (1 << 1)
+#define LEVT_SIGRAISE (1 << 2)
+
+typedef struct rbuffer** lbuf_ref_t;
+#define ref_current(lbuf) (&(lbuf)->current)
+#define ref_next(lbuf) (&(lbuf)->next)
+#define deref(bref) (*(bref))
+
+/**
+ * @brief Communication port capability that a device is supported natively,
+ * or able to emulate low level serial transmission behaviour specify
+ * by POSIX1-2008, section 11.
+ *
+ */
+#define TERMPORT_CAP 0x4d524554U
+
+/**
+ * @brief A termios capability that a device provide interfaces which is
+ * compliant to POSIX1-2008
+ *
+ */
+#define TERMIOS_CAP 0x534f4954U