problem with relationship

Let's say I have 3 models. Doctor, Area and Area_subspecialty.

My tables.

		public function up() {
				Schema::create('doctors', function (Blueprint $table) {
				$table->id();
				$table->timestamps();
				$table->foreignId('area_id')->constrained();
				$table->string('colmedico')->nullable()->unique();
				$table->string('abreviatura');
			});
		}

		public function up() {
				Schema::create('areas', function (Blueprint $table) {
				$table->id();
				$table->timestamps();
				$table->string('nomarea')->unique();
				$table->foreignId('departamento_id')->constrained();
			});
		}

		public function up() {
				Schema::create('area_especials', function (Blueprint $table) {
				$table->id();
				$table->timestamps();
				$table->foreignId('area_id')->constrained();
				$table->string('nombespeciali')->unique();
			});
	 }

My Models

	class Doctor extends Model {
		public function cualespeci(){
		return $this->hasOne(Area::class, 'id','area_id');
		}
	}

class Area extends Model {
	public function doctoarea(){
	  return $this->belongsTo(Doctor::class,'area_id');
  }

class AreaEspecial extends Model {
	public function larea() {
			return $this->belongsTo(Area::class, 'area_id');
}

A doctor belongs to an area, but a doctor can be assigned to several sub_areas, my problem is that I don't know how to get the areas_subspecialties that belong to a doctor, can someone please help me?

if I look for a Doctor. Example $d= Doctor::find(1); I get the data of the doctor and if I want to see which area he belongs to I do $d->cualespeci and I get the area to which he belongs now I just have to know which areas_subspecialties he belongs to.

sorry for my English