Spanking Reference in a Mainstream Novel ...

A couple of Clavell’s books have some reference, including Tai Pan, and King Rat, and I think maybe Shogun. Many of Wilbur Smiths books do as well.

There are several spanking references in Starship Troopers. The book, not the movie. And Harry Turtledove puts some into his series The Great War.

There are a couple of references in Trevanian's The Eiger Sanction. At one point Hemlock tells his cute neighbour who has appeared partially nude in his bed that he should spank her ass and he tells another woman who asks him what he deems an inappropriate question that he should smack her bottom. He even muses on how terribly in need of a spanking another character it.

Dana Fuller Ross has a spanking in Wyoming! , the third in her Wagons West series in the 70s and 80s. A hot-tempered minx gets spanked when she pulls a knife on a man who is trying his best to be her friend. It,works,they become friends, and she later saves his life in a fight with an outlaw. Couple of mentions or references to spankings in other books in this series too.
And surprised no one has mentioned Scout getting spanked in To Kill A Mockingbird(the book not the movie). Her uncle Jack spanks her for getting in a fight with her obnoxious cousin Francis because he said horrible things about Atticus. Jack and Scout make up and she explains why she attacked him. Jack is ready to go after Francis, but Scout persuades him to drop the matter because of a promise she made to Atticus.
Too bad,as if you read the book, you'd probably agree that Francis needed a gridhole paddle or something applied to his bare seat so that he would have been eating off the mantel for awhile!

One of the first spanking references I recall was reading the entire poem, Jack and Jill. The poem ends with the following lines:

Their mother vexed
Did whip her next
For causing Jack's disaster.

Batman
Yes, nursery rhymes were always good for spanking references. There was a little girl who had a little curl ends with the mother ‘did spank her most emphatic’, the old women who lived in a shoe ‘whipped them all soundly’, the king of hearts ‘beat the knave fullsore’… etc

Some of us infant perverts poured over our illustrated books of nursery rhymes in great delight.

An early memory was a Judge Dee mystery called the Phantom of the Temple by Robert van Gulik. The priestess of the temple regularly punished her assistant. The assistant recounts how

"she commands me to let down my trousers, bend for the Lord Buddha and pray for improvement of character. Then she lets me have it with a thin rattan, counting the strokes on an abacus".

A couple of pages later she talks about quitting her job and she says "let her pink another's girl's behind".

Over 50 years later, I can still recall these references as this was a formative experience about aged 12. The other literary reference I can remember from even earlier was Noddy getting spanked.

Robert A Heinlein in Glory Road. He also has referenced spanking in some of his other books.

In the book City of Ember it is mentioned that a teacher uses a paddle on misbehaving students.

Shadowspnk
Some? Try most. I don't think the man managed to go very long without inserting a spanking reference somewhere.