diff --git a/hw/display/sm501.c b/hw/display/sm501.c
index 79bd7bc2d1..66a1bfbe60 100644
--- a/hw/display/sm501.c
+++ b/hw/display/sm501.c
@@ -1930,7 +1930,7 @@ typedef struct {
     SM501State state;
     uint32_t vram_size;
     uint32_t base;
-    void *chr_state;
+    SerialMM serial;
 } SM501SysBusState;
 
 static void sm501_realize_sysbus(DeviceState *dev, Error **errp)
@@ -1938,6 +1938,7 @@ static void sm501_realize_sysbus(DeviceState *dev, Error **errp)
     SM501SysBusState *s = SYSBUS_SM501(dev);
     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
     DeviceState *usb_dev;
+    MemoryRegion *mr;
 
     sm501_init(&s->state, dev, s->vram_size);
     if (get_local_mem_size(&s->state) != s->vram_size) {
@@ -1958,15 +1959,15 @@ static void sm501_realize_sysbus(DeviceState *dev, Error **errp)
     sysbus_pass_irq(sbd, SYS_BUS_DEVICE(usb_dev));
 
     /* bridge to serial emulation module */
-    serial_mm_init(&s->state.mmio_region, SM501_UART0, 2,
-                   NULL, /* TODO : chain irq to IRL */
-                   115200, s->chr_state, DEVICE_LITTLE_ENDIAN);
+    qdev_init_nofail(DEVICE(&s->serial));
+    mr = sysbus_mmio_get_region(SYS_BUS_DEVICE(&s->serial), 0);
+    memory_region_add_subregion(&s->state.mmio_region, SM501_UART0, mr);
+    /* TODO : chain irq to IRL */
 }
 
 static Property sm501_sysbus_properties[] = {
     DEFINE_PROP_UINT32("vram-size", SM501SysBusState, vram_size, 0),
     DEFINE_PROP_UINT32("base", SM501SysBusState, base, 0),
-    DEFINE_PROP_PTR("chr-state", SM501SysBusState, chr_state),
     DEFINE_PROP_END_OF_LIST(),
 };
 
@@ -1997,9 +1998,20 @@ static void sm501_sysbus_class_init(ObjectClass *klass, void *data)
     dc->props = sm501_sysbus_properties;
     dc->reset = sm501_reset_sysbus;
     dc->vmsd = &vmstate_sm501_sysbus;
-    /* Note: pointer property "chr-state" may remain null, thus
-     * no need for dc->user_creatable = false;
-     */
+}
+
+static void sm501_sysbus_init(Object *o)
+{
+    SM501SysBusState *sm501 = SYSBUS_SM501(o);
+    SerialMM *smm = &sm501->serial;
+
+    sysbus_init_child_obj(o, "serial", smm, sizeof(SerialMM), TYPE_SERIAL_MM);
+    qdev_set_legacy_instance_id(DEVICE(smm), SM501_UART0, 2);
+    qdev_prop_set_uint8(DEVICE(smm), "regshift", 2);
+    qdev_prop_set_uint8(DEVICE(smm), "endianness", DEVICE_LITTLE_ENDIAN);
+
+    object_property_add_alias(o, "chardev",
+                              OBJECT(smm), "chardev", &error_abort);
 }
 
 static const TypeInfo sm501_sysbus_info = {
@@ -2007,6 +2019,7 @@ static const TypeInfo sm501_sysbus_info = {
     .parent        = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(SM501SysBusState),
     .class_init    = sm501_sysbus_class_init,
+    .instance_init = sm501_sysbus_init,
 };
 
 #define TYPE_PCI_SM501 "sm501"
diff --git a/hw/sh4/r2d.c b/hw/sh4/r2d.c
index ee0840f380..72bb5285cc 100644
--- a/hw/sh4/r2d.c
+++ b/hw/sh4/r2d.c
@@ -272,7 +272,7 @@ static void r2d_init(MachineState *machine)
     busdev = SYS_BUS_DEVICE(dev);
     qdev_prop_set_uint32(dev, "vram-size", SM501_VRAM_SIZE);
     qdev_prop_set_uint32(dev, "base", 0x10000000);
-    qdev_prop_set_ptr(dev, "chr-state", serial_hd(2));
+    qdev_prop_set_chr(dev, "chardev", serial_hd(2));
     qdev_init_nofail(dev);
     sysbus_mmio_map(busdev, 0, 0x10000000);
     sysbus_mmio_map(busdev, 1, 0x13e00000);