How can I get products with sub-category assigned?

How can I get products that have a sub-category assigned?

I have tables: products, magazine_subcategories and pivot table magazine_category_subcategory.

Before I created the sub-category I used this:

$query = Input::get('s');
Product::where('nazwa', 'like', '%' . $query . '%');

I have a $subcategory variable from the paramete.

Route::get('/magazine/{category}/{subcategory}', 'SearchController@sklep_kat_sub');

Model Magazine_subcategory

class Magazine_subcategory extends Model
{
    protected $fillable = [ 'name' ];

    public function categories()
    {
        return $this->belongsToMany('App\Magazine_category', 'magazine_category_subcategory',  'subcategory_id', 'category_id');
    }

    public function products()
    {
        return $this->belongsToMany('App\Product');
    }
}

Model Product

class Product extends Model
{


    protected $fillable = [
        'nazwa',
        'cena',
        'kopis',
        'dopis',
        'n_img',
        'subkategoria',
    ];

    public function subcategories()
    {
        return $this->belongsToMany('App\Magazine_subcategory', 'product_subcategory', 'product_id', 'subcategory_id');
    }
}