Where relation value higher than entity value with Eloquent

I have two entities; Part and PartStock. There is a one-to-one relationship between them:

Part model:

public function partStock()
{
    return $this->hasOne('App\PartStock');
}

PartStock model:

public function part()
{
    return $this->belongsTo('App\Part');
}

How can I write a global scope for Part that has a where filter for values on the PartStock relation and Part entity itself?

$query->where(???, '>', 'reorder');

$query->whereHas('partStock', function($q) {
    $q->where('count', '>', ???);
});

via Chebli Mohamed