diff --git a/kernel_module/README.md b/kernel_module/README.md
index a527dc3..3bdf434 100644
--- a/kernel_module/README.md
+++ b/kernel_module/README.md
@@ -27,4 +27,5 @@
     1.  [character_device](character_device.c)
     1.  Hardware device drivers
         1. [pci](pci.c)
+        1. [platform_device](platform_device.c)
 1.  [user](user/)
diff --git a/kernel_module/platform_device.c b/kernel_module/platform_device.c
new file mode 100644
index 0000000..f7f7766
--- /dev/null
+++ b/kernel_module/platform_device.c
@@ -0,0 +1,113 @@
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+
+MODULE_LICENSE("GPL");
+
+static struct resource res;
+static unsigned int irq;
+static void __iomem *map;
+
+static irqreturn_t lkmc_irq_handler(int irq, void *dev)
+{
+	pr_info("lkmc_irq_handler irq = %d dev = %llx\n", irq, *(unsigned long long *)dev);
+	/* ACK the IRQ. */
+	iowrite32(0x9ABCDEF0, map + 4);
+	return IRQ_HANDLED;
+}
+
+static int lkmc_platform_device_probe(struct platform_device *pdev)
+{
+	int asdf;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+
+	dev_info(dev, "probe\n");
+
+	/* Play with our custom poperty. */
+	if (of_property_read_u32(np, "lkmc-asdf", &asdf) ) {
+		dev_err(dev, "of_property_read_u32\n");
+		return -EINVAL;
+	}
+	if (asdf != 0x12345678) {
+		dev_err(dev, "asdf = %llx\n", (unsigned long long)asdf);
+		return -EINVAL;
+	}
+
+	/* IRQ. */
+	irq = irq_of_parse_and_map(dev->of_node, 0);
+	if (request_irq(irq, lkmc_irq_handler, 0, "lkmc_platform_device", dev) < 0) {
+		dev_err(dev, "request_irq");
+		return -EINVAL;
+	}
+	dev_info(dev, "irq = %u\n", irq);
+
+	/* MMIO. */
+	if (of_address_to_resource(pdev->dev.of_node, 0, &res)) {
+		dev_err(dev, "of_address_to_resource");
+		return -EINVAL;
+	}
+	if  (!request_mem_region(res.start, resource_size(&res), "lkmc_platform_device")) {
+		dev_err(dev, "request_mem_region");
+		return -EINVAL;
+	}
+	map = of_iomap(pdev->dev.of_node, 0);
+	if (!map) {
+		dev_err(dev, "of_iomap");
+		return -EINVAL;
+	}
+	dev_info(dev, "res.start = %u resource_size = %llx\n",
+			res.start, (unsigned long long)resource_size(&res));
+
+	/* Test MMIO and IRQ. */
+	iowrite32(0x12345678, map);
+
+	return 0;
+}
+
+static int lkmc_platform_device_remove(struct platform_device *pdev)
+{
+	dev_info(&pdev->dev, "remove\n");
+	free_irq(irq, &pdev->dev);
+	/* TODO free iomap. */
+	release_mem_region(res.start, resource_size(&res));
+	return 0;
+}
+
+static const struct of_device_id of_lkmc_platform_device_match[] = {
+	{ .compatible = "lkmc_platform_device", },
+	{},
+};
+
+MODULE_DEVICE_TABLE(of, of_lkmc_platform_device_match);
+
+static struct platform_driver lkmc_plaform_driver = {
+	.probe      = lkmc_platform_device_probe,
+	.remove	    = lkmc_platform_device_remove,
+	.driver     = {
+		.name   = "lkmc_platform_device",
+		.of_match_table = of_lkmc_platform_device_match,
+		.owner = THIS_MODULE,
+	},
+};
+
+static int lkmc_platform_device_init(void)
+{
+	pr_info("lkmc_platform_device_init\n");
+	return platform_driver_register(&lkmc_plaform_driver);
+}
+
+static void lkmc_platform_device_exit(void)
+{
+	pr_info("lkmc_platform_device_exit\n");
+	platform_driver_unregister(&lkmc_plaform_driver);
+}
+
+module_init(lkmc_platform_device_init)
+module_exit(lkmc_platform_device_exit)