I want a board I'm designing to accept either 5V or 3.3V power as input. If 5V power is supplied I want to generate 3.3V regulated power on board. The rest of the board all runs off of the 3.3V power. If I call my input power VDDIO, and VDDIO = 5V, then I know I can stick an LDO in there to get my 3.3V for the board. My question then is how do I allow for the case of regulated 3.3V input power.
One solution I thought of was to put in a normally-open solder jumper between Vin and Vout of the LDO, to let someone manually bypass the LDO. A more accessible direct analogy to this would be to include a bypass switch. But I'm interested in whether there may be a more elegant way to achieve the same effect "automatically", or whether the LDO will "handle" this for me already (i.e. if regulated 3.3V is fed into it, maybe it will just pass through to the output).