Yeah, simply regulating it down with an LDO will do. You need enough voltage rating of course. This comes to mind:
https://www.digikey.com/product-detail/en/on-semiconductor/NCV4274AST33T3G/NCV4274AST33T3GOSCT-ND/1967234Though maybe its low voltage startup isn't enough, I haven't checked. The 40V rating is typical of automotive parts, also see offerings by Infineon and others. Many of which tolerate negative input and output, too.
15V dropping to 3.3V is 12V, at 100mA is 1.2W -- a small SMT part won't be able to sustain that for long. If this is a momentary overload situation, that's fine; if the reg has a thermal limit built in it will cut off the load to reduce power, then cycle. The SOT-223 above, will handle it continuous, under typical conditions and given some thermal pours. SOT-89 similarly, SOIC-8 maybe maybe not, and anything through-hole with a heatsink tab definitely.
For more demanding applications, you might construct your own out of bigger parts -- a depletion mode MOSFET for example, can be used as a normally-on switch, biasing its gate to drain with a resistor. (It's wired as a source follower.) With a zener from GND to gate, its gate voltage is clamped at some voltage, and therefore its source will never be many volts above that. With a precision reference (TL431 or the like) this can be improved to a proper accurate threshold (given some limitations in response time, which might be addressable with filtering). I'm not sure how big DMOS are available (10s of W, maybe not 100s?), but they are available in quite high voltages, and can be stacked (cascoded) for arbitrarily high voltage standoff!
Tim