Most OEM applications utilize splash lubrication for this. Some high end rods and manfacturers have a very small (EDM) hole that runs lengthwise in the rod from the upper bearing saddle to the wrist pin bore in the rod. Pressurized
oil is then carried to the upper regions of the pin bore. Some also have squirters that direct pressurized
oil from the lower regions of the block to the bottom of the pistons in an effort to cool them but some splash provides a lubrication source also. Sometimes there are also gooves machined in the wrist pin bore in the piston that carries
oil scraped by the oil rings from the cylinder walls. Either way it does a tough job that is often not given much thought.