This feature is available only in the Universal Rendering Pipeline
The Planar Reflection Caster Decal is a special class that allows you to add real-time planar reflections to a decal with a compatible shader. A demo decal shader with support for reflections is provided.
Its functionality is in essence the same as a normal Planar Reflection Caster component, but due to the way that Decal Projectors work you can only assign a single reflection to a single material. If you want different decals with the same material to show different reflections (for example, multiple puddles in different rooms / floors ) you will need to use material variants to ensure that the reflections assigned to one decal do not override the reflection of another one with the same material.
Also, because Decals do not invoke the OnWillRenderObject function in Unity (as they are not really meshes nor usual renderers) having a reflective decal in the scene tied to a reflection renderer will disable the visibility optimizations in said Reflection Renderer, triggering its update whether decals and other reflective objects are visible or not.