This is not quite correct. Nokia listed "Nokian renkaat" as a separate company in Helsinki Stock Market in 1995. Today, the companies are fully independent publicly traded companies and have practically no connections.
So, yes, Nokia makes cell phones. And, yes, Nokian tires has been owned by the same Nokia that today is an IT company. But Nokia has not fully owned the Nokian tires for the last 10 years or so. Nokia has been a larger shareholder, but sold its remaining share to Bridgestone in 2003.
So, it would be more accurate to claim that "Nokian tyres are made by Bridgestone" than that "Nokian tyres are made by Nokia, the cell phone company." But still, both are wrong. The correct statement is more simple: Nokian tyres are made by Nokian tyres (Nokian Renkaat Oyj).