source-code/desktopRuntime/resources/assets/minecraft/atlases/banner_patterns.json

{
  "sources": [
    {
      "type": "minecraft:single",
      "resource": "minecraft:entity/banner_base"
    },
    {
      "type": "minecraft:directory",
      "prefix": "entity/banner/",
      "source": "entity/banner"
    }
  ]
}