-- selected render target
local renderTargetNode = octane.project.getSelection()[1]

-- use getInputNode instead of getConnectedNode (this way we kan skip linker nodes)
local kernelNode = renderTargetNode:getInputNode(octane.P_KERNEL)

print(kernelNode)

-- figure out the type of kernel (you can use .type here)
if kernelNode ~= nil then
    if kernelNode.type == octane.NT_KERN_DIRECTLIGHTING
    or kernelNode.type == octane.NT_KERN_PATHTRACING 
    or kernelNode.type == octane.NT_KERN_PMC
    or kernelNode.type == octane.NT_KERN_INFO
    or kernelNode.type == octane.NT_KERN_MATPREVIEW 
    then
        print(string.format("kernel with %d samples/px",
                            kernelNode:getPinValue(octane.P_MAX_SAMPLES)))
    else
        print("unknown kernel", kernelNode.type)
    end
else
    print("no kernel node connected to the render target")
end