docs: add supported hardware document

resolves #23.

docs/7.supported-hardware.md

@@ -0,0 +1,37 @@
+# Supported Hardware
+
+## Hardware SDR Sources/Sinks
+
+### Sources
+
+* [`RtlSdrSource`](0.reference-manual.md#rtlsdrsource) via [librtlsdr](http://sdr.osmocom.org/trac/wiki/rtl-sdr)
+* [`AirspySource`](0.reference-manual.md#airspysource) via [libairspy](https://github.com/airspy/host)
+* [`HackRFSource`](0.reference-manual.md#hackrfsource) via [libhackrf](https://github.com/mossmann/hackrf/tree/master/host/libhackrf)
+* [`SDRplaySource`](0.reference-manual.md#sdrplaysource) via [libmirsdrapi-rsp](http://sdrplay.com/linux.html)
+
+Coming soon:
+
+* [`BladeRFSource`](https://github.com/vsergeev/luaradio/issues/19)
+
+### Sinks
+
+None to date. All transceivers above planned.
+
+## File Sources/Sinks
+
+File sources and sinks can also indirectly support SDR hardware by a reading or
+writing a named pipe, linked to an external utility that interfaces with the
+SDR hardware.
+
+### Sources
+
+* [`IQFileSource`](0.reference-manual.md#iqfilesource) for binary I/Q files
+* [`RealFileSource`](0.reference-manual.md#realfilesource) for binary real-valued files
+* [`WAVFileSource`](0.reference-manual.md#wavfilesource) for WAV files
+
+### Sinks
+
+* [`IQFileSink`](0.reference-manual.md#iqfilesink) for binary I/Q files
+* [`RealFileSink`](0.reference-manual.md#realfilesink) for binary real-valued files
+* [`WAVFileSink`](0.reference-manual.md#wavfilesink) for WAV files
+