apply that patch:
diff --git a/arch/arm/mach-omap2/board-tuna.c b/arch/arm/mach-omap2/board-tuna.c
index a022a43..7098227 100644
--- a/arch/arm/mach-omap2/board-tuna.c
+++ b/arch/arm/mach-omap2/board-tuna.c
@@ -1001,6 +1001,8 @@ static inline void __init board_serial_init(void)
        omap_serial_init_port_pads(0, uart1_pads, uart1_pads_sz, NULL);
        omap_serial_init_port_pads(1, tuna_uart2_pads,
                ARRAY_SIZE(tuna_uart2_pads), &tuna_uart2_info);
+       omap_serial_init_port_pads(2,tuna_uart3_pads,
+               ARRAY_SIZE(tuna_uart3_pads), NULL);
        omap_serial_init_port_pads(3, tuna_uart4_pads,
                                   ARRAY_SIZE(tuna_uart4_pads), NULL);
 }