Documentation: Add docummentation to AVR32DEV1/UC3B-CPU board.

This commit add documentation to the UC3B-CPU board, this is
board is a clone of Atmel AVR32DEV1.

Signed-off-by: Alan C. Assis <acassis@gmail.com>

Documentation/platforms/avr/at32uc3/boards/avr32dev1/index.rst

@@ -2,9 +2,40 @@
 avr32dev1
 =========
 
-This is a port of NuttX to the Atmel AVR32DEV1 board.  That board is
-based on the Atmel AT32UC3B0256 MCU and uses a specially patched
-version of the GNU toolchain:  The patches provide support for the
+This is a port of NuttX to the Atmel AVR32DEV1 board and compatible
+with MCUZone UC3B-CPU board depicted here:
+
+.. figure:: mcuzone_uc3b-cpu.png
+   :align: center
+
+This board is based on the Atmel AT32UC3B0256 MCU and uses a specially
+patched version of the GNU toolchain:  The patches provide support for the
 AVR32 family.  That patched GNU toolchain is available only from the
-Atmel website.  STATUS: This port is functional but very basic.  There
+Atmel website.
+
+STATUS: This port is functional but very basic. There
 are configurations for NSH and the OS test.
+
+Features
+========
+
+  - AVR32 AT32UC3B0256 microcontroller
+  - mini-USB Connector
+  - Power LED (LED1)
+  - MCU controllable LEDs: LED2 and LED3
+  - S1/RESET and S2 buttons (S2 accessible to user)
+  - 12MHz (main clock) and 32KHz for RTC
+
+Serial Console
+==============
+
+The board uses by default the USART1 as serial console.
+The pins PB2 (TXD) and PA24 (RXD) are used for USART1.
+
+This way you need to connect a USB/Serial adapter to
+get access to the NuttShell. Connect the TXD from your
+USB/Serial to the RXD of the board, and the RXD from
+USB/Serial to the TXD of the board.
+
+There is another detail about the baudrate, you need to
+use 57600 8n1.