diff --git a/arch/arm/include/stdarg.h b/arch/arm/include/stdarg.h
new file mode 100644
index 0000000000..653d34a6ff
--- /dev/null
+++ b/arch/arm/include/stdarg.h
@@ -0,0 +1,59 @@
+/****************************************************************************
+ * arch/arm/include/stdarg.h
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __ARCH_ARM_INCLUDE_STDARG_H
+#define __ARCH_ARM_INCLUDE_STDARG_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+/* This should work with any modern gcc (newer than 3.4 or so) */
+
+#define va_start(v,l)   __builtin_va_start(v,l)
+#define va_end(v)       __builtin_va_end(v)
+#define va_arg(v,l)     __builtin_va_arg(v,l)
+#define va_copy(d,s)    __builtin_va_copy(d,s)
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+typedef __builtin_va_list va_list;
+
+#endif /* __ARCH_ARM_INCLUDE_STDARG_H */
diff --git a/arch/arm/src/lpc43xx/lpc43_serial.c b/arch/arm/src/lpc43xx/lpc43_serial.c
index d3f718d0a0..2d4ea9aac7 100644
--- a/arch/arm/src/lpc43xx/lpc43_serial.c
+++ b/arch/arm/src/lpc43xx/lpc43_serial.c
@@ -552,6 +552,9 @@ static inline void up_enablebreaks(struct up_dev_s *priv, bool enable)
  *   Configure the U[S]ART divisors to accomplish the desired BAUD given the
  *   U[S]ART base frequency.
  *
+ *   This computationally intensive algorithm is based on the same logic
+ *   used in the NXP sample code.
+ *
  ****************************************************************************/
 
 void up_setbaud(struct up_dev_s *priv)