function minetest.item_place(itemstack, placer, pointed_thing)
	-- Call on_rightclick if the pointed node defines it
	if pointed_thing.type == "node" and placer and
			not placer:get_player_control().sneak then
		local n = minetest.env:get_node(pointed_thing.under)
		local nn = n.name
		if minetest.registered_nodes[nn] and minetest.registered_nodes[nn].on_rightclick then
			return minetest.registered_nodes[nn].on_rightclick(itemstack,placer, pointed_thing.under, n)
		end
	end

	if itemstack:get_definition().type == "node" then
		return minetest.item_place_node(itemstack, placer, pointed_thing)
	elseif itemstack:get_definition().type ~= "none" then
		return minetest.item_place_object(itemstack, placer, pointed_thing)
	end
end

And example usage:

	on_rightclick = function(itemstack,clicker, pos, node)
		if itemstack:get_name() == "default:sign_wall" then
			fdir = minetest.dir_to_facedir(clicker:get_look_dir())
			minetest.env:add_node(pos, {name = "homedecor:fence_brass_with_sign", param2 = fdir})
			itemstack:take_item()
		return itemstack
		end
	end