net: Implement net_serial_devices

This function provides a platform-specific list of serial devices that
can be accessed.

src/net/inc/net/serial.h

@@ -0,0 +1,17 @@
+#ifndef NET_SERIAL_H
+#define NET_SERIAL_H
+
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+const char *const *net_serial_devices(size_t *n);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NET_SERIAL_H */

src/net/src/posix/serial.c

@@ -1,4 +1,5 @@
 #include <net.h>
+#include <net/serial.h>
 #include <net_private.h>
 #include <stddef.h>
 
@@ -42,3 +43,8 @@ int net_init_serial(void)
 void net_deinit_serial(void)
 {
 }
+
+const char *const *net_serial_devices(size_t *const n)
+{
+    return NULL;
+}

src/net/src/ps1/net.c

@@ -1,4 +1,5 @@
 #include <net.h>
+#include <net/serial.h>
 #include <errno.h>
 #include <stddef.h>
 
@@ -40,3 +41,14 @@ int net_init(void)
 void net_deinit(void)
 {
 }
+
+const char *const *net_serial_devices(size_t *const n)
+{
+    static const char *const dev[] =
+    {
+        "PS1 port"
+    };
+
+    *n = sizeof dev / sizeof *dev;
+    return dev;
+}

src/net/src/win9x/serial.c

@@ -42,3 +42,8 @@ int net_init_serial(void)
 void net_deinit_serial(void)
 {
 }
+
+const char *const *net_serial_devices(size_t *const n)
+{
+    return NULL;
+}