Doc/xtensa/esp32: Add documentation to Heltec WiFi LoRa32

This commit adds documentation to Heltec WiFi LoRa32

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

Documentation/platforms/xtensa/esp32/boards/heltec_wifi_lora32/index.rst

@@ -0,0 +1,89 @@
+======================
+Heltec WiFi LoRa 32 V2
+======================
+
+.. tags:: chip:esp32, chip:esp32wrover32
+
+The Heltec WiFi LoRa32 is a development board based on an ESP32 microcontroller. It is designed for LoRa application.
+
+.. list-table::
+   :align: center
+
+   * - .. figure:: wifi-lora-32-v2.png
+          :align: center
+
+          Heltec WiFi LoRa32 V2
+
+Features
+========
+
+  - ESP32 (240MHz Tensilica LX6 dual-core+1 ULP, 600 DMIPS)
+  - LoRa Node Chip SX1276/SX1278
+  - OLED Display 
+  - Battery Charger 3.7V lithium (SH1.25 x 2 socket)
+  - LoRa ANT(IPEX1.0)
+
+Pinout
+======
+
+Most of I/O pins are broken out to the header pins as displayed here:
+
+.. list-table::
+   :align: center
+
+   * - .. figure:: wifi-lora-32-v2-pinout.png
+          :align: center
+
+          Heltec WiFi LoRa32 V2 Pinout
+
+Schematic
+=========
+
+https://resource.heltec.cn/download/WiFi_LoRa_32/V2/WiFi_LoRa_32_V2(433%2C470-510).PDF
+
+Serial Console
+==============
+
+UART0 is, by default, the serial console. It connects to the on-board
+CP2102 converter.
+
+Buttons and LEDs
+================
+
+Board Buttons
+-------------
+
+There are two buttons labeled BOOT and RST. The RST button is not available
+to software. It pulls the chip enable line that doubles as a reset line.
+
+The BOOT button is connected to IO0. On reset it is used as a strapping
+pin to determine whether the chip boots normally or into the serial
+bootloader. After reset, however, the BOOT button can be used for software
+input.
+
+Board LEDs
+----------
+
+There is one LED available connected to IO25.
+
+Configurations and Flashing
+===========================
+
+All of the configurations presented below can be tested by running the following commands::
+
+    $ ./tools/configure.sh heltec_wifi_lora32:<config_name>
+
+Where <config_name> is the name of board configuration you want to use, i.e.: nsh, buttons, wifi...
+
+Flashing is done in the default way for ESP32 boards using::
+
+    $ make flash ESPTOOL_PORT=/dev/ttyUSB0 -j
+
+Then use a serial console terminal like ``minicom`` or `picocom`` configured to 115200 8N1.
+
+nsh
+---
+
+Basic NuttShell configuration (console enabled in UART0, exposed via
+USB connection by means of CH340 converter, at 115200 bps).
+