Update README.md

Author: fpistm

README.md

@@ -3,13 +3,25 @@
 [![GitHub commits](https://img.shields.io/github/commits-since/stm32duino/Arduino_Core_STM32/1.3.0.svg)](https://github.com/stm32duino/Arduino_Core_STM32/compare/1.3.0...master)
 [![Build Status](https://travis-ci.com/stm32duino/Arduino_Core_STM32.svg?branch=master)](https://travis-ci.com/stm32duino/Arduino_Core_STM32)
 
-**Warning**: release versioning has been changed from date versioning to semantic one. See [Release Versioning change](https://github.com/stm32duino/wiki/wiki/Release-Versioning-change)
-
+* [Introduction](https://github.com/stm32duino/Arduino_Core_STM32#Introduction)<br>
 * [Getting Started](https://github.com/stm32duino/Arduino_Core_STM32#getting-started)<br>
 * [Boards available](https://github.com/stm32duino/Arduino_Core_STM32#boards-available)<br>
 * [Troubleshooting](https://github.com/stm32duino/Arduino_Core_STM32#troubleshooting)<br>
 * [Wiki](https://github.com/stm32duino/wiki/wiki/)
 
+## Introduction
+
+This repo adds the support of STM32 MCU in Arduino IDE.<br>
+
+This porting is based on:
+* [STM32Cube MCU Packages](https://www.st.com/en/embedded-software/stm32cube-mcu-packages.html) including:
+    * The HAL hardware abstraction layer, enabling portability between different STM32 devices via standardized API calls
+    * The Low-Layer (LL) APIs, a light-weight, optimized, expert oriented set of APIs designed for both performance and runtime efficiency
+    * CMSIS device defintion for STM32
+* [CMSIS](https://developer.arm.com/embedded/cmsis): Cortex Microcontroller Software Interface Standard (CMSIS) is a vendor-independent hardware abstraction layer for the Cortex®-M processor series and defines generic tool interfaces. It has been packaged as a module for Arduino IDE: https://github.com/stm32duino/ArduinoModule-CMSIS
+* [GNU Arm Embedded Toolchain](https://developer.arm.com/open-source/gnu-toolchain/gnu-rm): Arm Embedded GCC compiler, libraries and other GNU tools necessary for bare-metal software development on devices based on the Arm Cortex-M. Packages are provided thanks: https://github.com/stm32duino/arm-none-eabi-gcc
+
+
 ## Getting Started
 
 This repo is available as a package usable with [Arduino Boards Manager](https://www.arduino.cc/en/guide/cores).
@@ -21,7 +33,9 @@ https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_ind
 
 For full instructions on using the "**Boards Manager**", see the [Getting Started](https://github.com/stm32duino/wiki/wiki/Getting-Started) page.
 
-For advanced user, you can use the repository: see the [Using git repository](https://github.com/stm32duino/wiki/wiki/Using-git-repository) page.
+Advanced user can use the repository to benefit from the latest development. See the [Using git repository](https://github.com/stm32duino/wiki/wiki/Using-git-repository) page.
+
+User can add a STM32 based board following this [wiki](https://github.com/stm32duino/wiki/wiki/Add-a-new-variant-(board)).
 
 ## Boards available
 ### Current release