There are many good reasons to buy NXP Semiconductors (NASDAQ:NXPI) shares today. But one of the many upsides stands head and shoulders above the others. I'm talking about the analog-chip maker's stranglehold on the exploding market for automotive computing processors.

But I thought NXP was a mobile payments expert

Not what you expected? I understand. Many investors automatically associate NXP with near-field communications, or NFC, chips.

That technology powers smartphone-based payment systems and other close-range information data streams with high security. NXP didn't exactly invent it -- NFC was approved as an international standard, while NXP still was the semiconductor arm of Philips, which worked together with Sony to establish the platform. But in recent years, NXP has certainly taken the reins on NFC development and commercialization and is the undisputed market leader for these chips.

That being said, NFC products are not a major growth driver for NXP. They are rolled up in the secure connected devices division alongside other low-energy communications solutions, environmental sensors, wireless security, and embedded microcontrollers. When the merger with Freescale closed earlier this year, that company's successful microcontroller business further diluted NFC's impact on the combined company's results.

I think it speaks volumes that NXP's recent first-quarter report didn't specifically mention NFC sales at all. And when one analyst tried to poke at that sleeping bear on the earnings call, CEO Rick Clemmer dodged the question and artfully turned the discussion onto automotive sales in China instead.

It's all about automotive

That is indeed the big show at NXP today. Adding Freescale's large market share in automotive chips to NXP's own fledgling position has created the leading player in a very promising sector. According to market research firm Strategy Analytics, the company holds a 14.2% share of a $27.4 billion global market. No other company has more than a 10.4% share.

Modern cars are handling more and more computing tasks. Infotainment systems need processors. So do engine optimization technologies, safety systems, and the trend toward in-car networking. That's before thinking ahead to self-driving cars or all-electric vehicles.

So in an era of slipping semiconductor sales, dying PC markets, and slowing growth in mobile devices, automotive chips are in high demand. The market has grown 19% over the last four years, and the real hockey-stick growth curve still appears to lie ahead. The car market itself doesn't even have to expand much in order to make this work, as long as computers keep invading our garages.

All told, the automotive division was the only segment to report true year-over-year growth in the first quarter. As I said, many stalwart technology growth markets are suffering right now. It's also NXP's largest division, pulling in an unmatched 36% of the company's total quarterly sales. No other division (including that vaunted NFC-packing secure connected devices arm) crossed the 22% threshold.

So automotive products offer NXP's fastest proven growth plus the largest upcoming market opportunity, and all of that is built on top of the company's biggest existing operation. What's not to love?

You simply cannot understand NXP before getting a grip on the automotive opportunity. This is where the rubber meets the road.