[HAT] Update overview page

Author: AksonovSergei

docs/platform/rpi_power_hat/overview.md

@@ -1,6 +1,20 @@
 # Overview
 
-- [ ] TODO Add description
+# Overview
 
 ![RPI Power HAT](./img/rpihat_v1.png)
 
+## Main Characteristics
+
+| Characteristic       | Value       |
+|----------------------|-------------|
+| Input Voltage        | 6V-40V      |
+| Output Voltage       | 5.1V        |
+| Max Output Current   | 5A          |
+
+## Documentation
+* [Requirements specification](./requirements.md)
+* [Schematic pdf](https://github.com/KPI-Rover/rpi-power-hat/releases/download/Releases%2FVersion1.0/KPI-Rover_RPI_Power_HAT_schematic.pdf)
+* [GitHub Repository](https://github.com/KPI-Rover/rpi-power-hat)
+
+