Add serial on ARC platform.

include/grub/serial.h

@@ -30,6 +30,9 @@
 #ifdef GRUB_MACHINE_IEEE1275
 #include <grub/ieee1275/ieee1275.h>
 #endif
+#ifdef GRUB_MACHINE_ARC
+#include <grub/arc/arc.h>
+#endif
 
 struct grub_serial_port;
 struct grub_serial_config;
@@ -104,6 +107,13 @@ struct grub_serial_port
 #endif
 #ifdef GRUB_MACHINE_EFI
     struct grub_efi_serial_io_interface *interface;
+#endif
+#ifdef GRUB_MACHINE_ARC
+    struct
+    {
+      grub_arc_fileno_t handle;
+      int handle_valid;
+    };
 #endif
   };
   grub_term_output_t term_out;
@@ -170,6 +180,12 @@ void grub_ofserial_init (void);
 void
 grub_efiserial_init (void);
 #endif
+#ifdef GRUB_MACHINE_ARC
+void
+grub_arcserial_init (void);
+const char *
+grub_arcserial_add_port (const char *path);
+#endif
 
 struct grub_serial_port *grub_serial_find (const char *name);
 extern struct grub_serial_driver grub_ns8250_driver;