SerialPort() can't open UARTx type ports of ARM platforms, only works with COMx

This is a bummer as it forces IoT and UWP developers to maintain two versions of a serial interface depending on which platform the application will run x86 or ARM. Nothing UNIVESAL about this one.

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#### Document Details

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* ID: fa765d00-19f8-74e4-4be1-1d7f1e7dc6ce
* Version Independent ID: 260749e3-69c6-a370-89b0-4f90d944fac7
* Content: [SerialPort Class (System.IO.Ports)](https://docs.microsoft.com/en-us/dotnet/api/system.io.ports.serialport?view=netframework-4.7.2)
* Content Source: [xml/System.IO.Ports/SerialPort.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.IO.Ports/SerialPort.xml)
* Product: **dotnet-api**
* GitHub Login: @mairaw
* Microsoft Alias: **mairaw**