Allow VFS file descriptors in select()

examples/peripherals/uart_select/README.md

@@ -0,0 +1,13 @@
+# UART Select Example
+
+The UART select example is for demonstrating the use of `select()` for
+synchronous I/O multiplexing on the UART interface. The example waits for a
+character from UART using `select()` until a blocking read without delay or a
+successful non-blocking read is possible.
+
+Please note that the same result can be achieved by using `uart_read_bytes()`
+but the use of `select()` allows to use it together with other virtual
+file system (VFS) drivers, e.g. LWIP sockets. For a more comprehensive example
+please refer to `system/select`.
+
+See the README.md file in the upper level 'examples' directory for more information about examples.